Protease-resistant thrombomodulin analogs

ABSTRACT

The present invention relates to the single-chain thrombomodulin (&#34;TM&#34;) and analogs thereof that are not susceptible to cleavage by proteases and retain the biological activity of thrombomodulin, as well as methods of use in, for example, antithrombotic therapy. Novel proteins, nucleic acid gene sequences, pharmaceuticals and methods of inhibiting thrombotic activity are disclosed.

This application is a Division of application Ser. No. 08/197,576 filedFeb. 16, 1994, which is a continuation of application Ser. No.07/830,577, filed Feb. 5, 1992, now abandoned, which is a continuationof 730,975, filed Jul. 29, 1991, now abandoned, which is acontinuation-in-part of U.S. Ser. No. 07/568,456, filed Aug. 15, 1990,now abandoned which is a continuation-in-part of U.S. Ser. No.07/506,325, filed Apr. 9, 1990, now U.S. Pat. No. 5,256,770, and theapplication corresponding to PCT Ser. No. 90/00955, filed Feb. 16, 1990,which was a continuation-in-part application of U.S. Ser. No.07/406,941, filed Sep. 13, 1989, now abandoned, which was acontinuation-in-part of U.S. Ser. No. 07/345,372, filed Apr. 28, 1989,now abandoned, all of whose disclosures are entirely incorporated byreference herein.

BACKGROUND OF THE INVENTION

The present invention relates to single-chain thrombomodulinpolypeptides, including analogs of thrombomodulin ("TM") that are lesssusceptible to cleavage by proteases. These analogs are useful in, forexample, antithrombotic therapy. Novel proteins, nucleic acid genesequences, pharmaceuticals, and methods of inhibiting thromboticactivity are disclosed.

There are many disease states that would benefit from treatment with asafe and effective anticoagulant/anti-thrombotic. The nature of theseconditions varies. For example, anticoagulant therapy is useful in acuteconditions such as during thrombolytic therapy in myocardial infarctionor in treatment of disseminated intravascular coagulation (DIC)associated with, for example, septicemia. Anticoagulants are also usefulfor less acute conditions, such as chronic use in patients that havereceived heart valve implants or prophylactic use in surgery patients toreduce the risk of deep venous thrombosis (DVT).

Thrombomodulin is a membrane protein that has demonstrated anticoagulantproperties. Its physiological importance has been studied. (See, forexample, N. Esmon, et al., (1982) J. Biol. Chem. 257:859-864, H. Salem,et al., (1983) J. Biol. Chem. 259:12246-12251).

The gene encoding native thrombomodulin has been isolated and sequencedfrom several species, both in its genomic form and as a CDNA clone(Jackman, R., et al., (1986) Proc. Natl. Acad. Sci. USA. 83:8834-8838and (1987) 84:6425-6429, both of which are herein incorporated byreference). Comparisons with known proteins, such as the LDL receptor,have suggested functional domains (Wen, D., et al., (1987) Biochemistry26:4350-4357). One study has suggested that the fifth and sixthepidermal growth factor (EGF)-like domains have the capacity to bindthrombin (Kurosawa, S., et al., (1988) J. Biol. Chem. 263:5993-5996;another suggests that EGF-like domains 4, 5, and 6 are sufficient to actas a cofactor for thrombin-mediated protein C activating activity.(Zushi, et al., (1989) J. Biol. Chem. 264:10351-10353). Inhibition ofthrombin's direct procoagulant activity (conversion of fibrinogen tofibrin) has been attributed in part to glycosaminoglycan substituents onthe thrombomodulin molecule. (Bourin, M. C. et al., (1986) Pro. Natl.Acad. Sci. USA 83:5924-5928.) The O-linked glycosylation domain haspotential sites for the addition of these types of sulfated sugars.

Thrombomodulin analogs, including soluble molecules, having variousmodifications are known. There are, for example, modifications tooxidation-sensitive amino acid residues in thrombomodulin which renderthe molecule resistant to oxidation. There are also modifications tothrombomodulin, e.g., by elimination of sulfated o-linked carbohydratesthrough enzymatic removal or modification of glycosylation sites on thepeptide, which decrease the inhibition of thrombin-mediated plateletaggregation and thrombin-mediated conversion of fibrinogen to fibrin,which is an important property of thrombin. These modifications aredisclosed in U.S. Ser. No. 07/568,456, filed Aug. 15, 1990, which isincorporated herein by reference.

Anticoagulants currently approved for use in humans are not uniformlyeffective and a need exists for more efficacious compounds (See, forexample, Prevention of Venous Thrombosis and Pulmonary Embolism,Consensus Development Conference Statement, NIH, 1986, 6(2):1-23).

Thrombomodulin in its native form is not suitable for anticoagulanttherapy as it is membrane-bound, due to its inherent amino acidsequence, and is insoluble without detergent treatment. It is present insuch small amounts (about 300 mg thrombomodulin/person) thatpurification from autopsy or biopsy samples is impractical.

Soluble thrombomodulin-like molecules have been detected at very lowamounts in human plasma and urine. These molecules have a reducedability to promote protein C activation, and it is possible that theyhave been rendered at least partially inactive, due at least in part, tooxidation. It has been suggested that these molecules are degradationproducts of the membrane bound molecule (Ishii, H. and Majerus, P.,(1985) J. Clin. Inv. 76:2178-2181), but they are present in such lowamounts that they have been difficult to characterize (˜0.8 mg/adultmale). Proteolytic fragments of the purified native molecule have beenproduced using trypsin or elastase. (See, Ishii, supra, Kurosawa, etal., (1988) J. Biol. Chem. 263:5593-5996 and Stearns, et al., (1989) J.Biol. Chem. 264:3352-3356). Some of these fragments retain the abilityto promote thrombin-mediated activation of protein C in vitro.

The production of TM and TM analogs by recombinant techniques inheterologous cells, e.g., in cell culture, has encountered numerousproblems in achieving acceptable products for use in in vivoapplications. For example, the N-terminal end of TM is impreciselycleaved in cells containing the recombinant gene as well as in nativecells, resulting in a product that has a non-unique N-terminus. Thiscauses, among other difficulties, a problem in providing proof of purityof the isolated polypeptide, e.g., for regulatory purposes.Glycosylation of recombinantly produced TM has also proved to be aproblem, in that some of the glycosylation sites are apparently involvedin maximizing biological activity, while other sites are apparentlyrecognized as signals in vivo to clear the bloodstream of TM, thusreducing the circulating half-life of a TM so glycosylated. Other, lesswell defined problems also are known to exist which interfere with theproduction of a maximally useful recombinantly produced TM polypeptide.

Thus, there is a need for new compositions that exhibit theanticoagulant properties of thrombomodulin and are easily produced inlarge quantities, but without the problems encountered in recombinantproduction of TM by heterologous cells. The present invention fulfillsthese and other needs.

SUMMARY OF THE INVENTION

This invention provides single-chain thrombomodulin (TM) substantiallydevoid of two-chain TM. This TM is provided by removal of two-chain TMfrom preparations which contain it, or by preventing cleavage ofsingle-chain TM.

In another embodiment, this invention excludes instances, if any, whereTM has been produced in a process which, heretofor unrecognizedly,inherently produced single-chain TM, substantially devoid of two-chainTM, e.g., wherein TM was produced under protein synthetic conditionswherein there is no protease capable of cleaving TM present or such aprotease, if present, did not contact the TM, or did so under conditionswhich did not allow cleavage, e.g., in the presence of a proteaseinhibitor effective to prevent the cleavage of TM; wherein TM has beenproduced and purified under conditions which serendipitously do notresult in cleavage, and wherein the effect of these conditions isunappreciated; wherein TM was produced by any applicable in vitrochemical synthetic means, e.g., solid phase synthesis under cell-freeconditions (if there are any such methods which could have been used toproduce TM); etc.

In another embodiment, this invention provides TM having a singleN-terminus. This TM is provided by the absence of two-chain TM, and/orby the elimination of the natural, heterogeneous N-terminal signalsequence processing site.

In another embodiment, this invention provides TM having a singleC-terminus. This TM is provided by the absence of a C-terminus which issensitive to exocarboxypeptidase.

In another embodiment, this invention provides single-chain TM which canbe expressed in eukaryotic cells, e.g., animal cells, vertebrate cells,insert cells mammalian cells, human cells, etc., e.g., in CHO or CHL1cells.

This invention provides methods for treating thrombotic disease byadministering an effective dose of a single-chain thrombomodulin oranalog thereof, typically one which is resistant to protease cleavageand which retains the biological activity of thrombomodulin. In somepreferred aspects, the polypeptide composition exhibits only a singleN-terminus and a single C-terminus, has at least approximately nativeability to potentiate thrombin-mediated activation of protein C, and/orhas a reduced ability to inactivate thrombin-mediated conversion offibrinogen to fibrin. It is preferred in some embodiments that theanalog is soluble in aqueous solution and/or has a long circulatinghalf-life, e.g., is oxidation and/or protease resistant.

In other embodiments, it is preferred that the analog be modified inthe-sugar residues of the O-linked glycosylation domain. By modified itis meant that the O-linked glycosylation domain has an alteredglycosylation pattern. This can encompass substitution, and total orpartial deletion of native sugar residues. This modification can beachieved by deleting the amino acid residues that are recognized bycells as glycosylation sites e.g., by site directed mutagenesis.Alternatively the sugars can be chemically removed, either partially ortotally. In another modification the sugars can be enzymatically treatedto remove sulfate substituents. In yet another modification the entireglycosylation domain can be deleted.

Some preferred analogs for use in the method will retain the capacity topotentiate the thrombin-mediated activation of protein C and/or have 80%or less of the capacity of native thrombomodulin to inactivatethrombin-mediated conversion of fibrinogen to fibrin. More specifically,these TM analogs, when standardized to have an equal activity in astandard protein C activation assay compared to nativedetergent-solubilized rabbit thrombomodulin, will have only 80% or lessof the activity of the same amount (mass) of native thrombomodulin in astandard assay measuring thrombin-mediated conversion of fibrinogen tofibrin. One preferred analog of this invention has 50% or less of theactivity of the same amount of native thrombomodulin in the fibrinassay. These capacities are measured using standard assays describedherein.

This invention further provides for sterile compositions for treatingthrombotic disease in mammals comprising a unit dosage of athrombomodulin analog having one or more of the above-noted properties.The preferred analogs are as described above for various methods.

This invention further provides for methods of increasing the in vivocirculating half-life of a thrombomodulin analog comprising removing allor most of the sugar moieties, e.g., in the 6 EGF-like domains.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 shows an elution and activity profile of a soluble TM_(E) (Sf9)preparation resolved on a Mono Q column.

FIG. 2 shows SDS-PAGE analysis of samples from the column profile shownin FIG. 1.

FIG. 3 shows gel electrophoresis profiles of samples run under reducingconditions.

FIG. 4 shows a Western blot of a gel electrophoresis profile.

FIG. 5 shows a double reciprocal plot of TM binding to thrombin.

DETAILED DESCRIPTION OF THE INVENTION

In accordance with the present invention, new TM analogs, methods, andcompositions are provided which can treat thrombotic disease. They arebased on a single-chain thrombomodulin (TM) or thrombomodulin analogwhich is resistant to protease cleavage, In addition, othermodifications can be introduced which result in other improvedproperties of an antithrombotically effective pharmaceutical, e.g.,wherein the TM exhibits a reduced capacity to inhibit the directprocoagulant activities of thrombin or exhibits other properties such asthrombin-mediated conversion of fibrinogen to fibrin, oxidationresistance, glycosylation resistance, increased in vivo half-life, etc.Pharmacologists prefer drugs which contain a single therapeuticallyeffective homogeneous composition. Such drugs are preferred because theyare less likely to induce undesired side effects than drugs containingmultiple species, including species containing undefined biologicaleffectiveness. This invention has the advantage of containing a morebiologically pure species, often also being chemically pure, which doesnot have the disadvantages of prior art products.

The prior art thrombomodulin compositions, particularly those producedby recombinant techniques in heterologous cells, have been studiedextensively by the present inventors in order to determine parametersfor the structure of the polypeptide which provide optimalpharmaceutical utility. In the course of these investigations, it wasfound that, surprisingly, thrombomodulin preparations previously thoughtto contain pure, single-chain polypeptides were, in fact, heavilycontaminated with thrombomodulin polypeptides having an internal peptidecleavage, but wherein the polypeptide continued to copurify withsingle-chain forms of TM, because the cysteine bonding between theseparate chains caused the two-chain form of the TM to behave similarlyto a single-chain form under purification conditions. This would applyboth to full-length native TM, as well as to soluble TM molecules.

This previously unappreciated problem was discovered, in part, bycareful analysis of these preparations, which revealed that therecombinantly produced thrombomodulin demonstrated two-phase non-linearbinding properties. Double plot analysis, indicated the presence of twospecies with different binding affinities in the composition. This ledto further investigations as to the nature of the different species.Careful analysis of TM preparations using sodium dodecylsulfate-polyacrylamide gel electrophoresis (SDS-PAGE) run underreducing, non-reducing, or native conditions and employing sensitivedetection techniques, e.g., silver or immunological staining, led to thediscovery that there was a second immunoreactive band having an apparentmolecular weight of about 80 kilodaltons, in addition to the expected 94kilodalton band of particular soluble TM analogs, on such gels. Thiscomposition was then shown to have a second N-terminal amino acidsequence consistent with the presence of an internal N-terminus. This islikely the result of a protease cleavage, at a location within the TMsequence, indicating that the apparently single-chain form of TM wascontaminated with a cleaved near or two-chain species. This species iscleaved within the thrombin binding site of the TM. Thus, while thephysical characteristics of the two-chain form were so similar to thesingle-chain form as to result in copurification, in fact the biologicalactivity, e.g., the binding properties, of the mixture appears to beaffected by this previously unrealized distinct species. The presentinvention provides thrombomodulin analog compositions substantially freeof such two-chain contaminants.

In another aspect of this invention, there are provided other improvedcompositions of thrombomodulin. For example, it has also been discoveredthat TM analogs, especially those produced by heterologous cells underrecombinant conditions have an N-terminus produced by signal sequenceprocessing of the amino acid sequences upstream of the matureN-terminus. In fact, the product exhibits heterogeneity at the aminoterminus. There are two processing sites, one which provides the nativeN-terminal amino acid 1, and a second site which, when used, produces acleavage product containing two more amino acids at the N-terminus,e.g., starting at amino acid -2. By modification of the DNA sequenceencoding the N-terminus of the TM polypeptide, the signal sequenceprocessing site can be modified to provide a single N-terminalprocessing site, and therefore a single N-terminus for the resultant TManalogs. Thus, a TM analog which deletes the first three amino acids ofthe native molecule provides a signal sequence processing site which isunique, thereby producing a polypeptide composition with a singleN-terminal sequence.

Still further, the elimination of internal cleavages to produce asingle-chain TM analog results in a composition having a homogeneouscarboxy terminus. Constructs which are resistant to protease or otherproteolytic cleavage are made so as to provide single C-termini as well.This can be accomplished by removal or modification of protease cleavagesites. For example, by deleting a portion of the C-terminal region ofthe polypeptide which is not critical to biological function inpharmaceutical applications, a polypeptide can be provided whichterminates in a -Pro-Pro sequence at amino acids 489-490, which sequenceis especially resistant to exocarboxypeptidase activity.

In another embodiment, this invention also provides for methods ofincreasing the in vivo half-life of TM analogs by modifying or deletingparticular native glycosylation patterns, or removing protease-sensitivesequences. Our early studies have indicated that theproteolysis-resistant form of soluble TM has a longer circulatinghalf-life in an animal. Thus, it is likely that a physiologicalmechanism which contributes to TM inactivation is proteolysis at, ornear, the identified region of the protein. By modifying this segment ofthe sequence to avoid inactivation, a much more effective therapeuticagent is produced. Increased half-life is advantageous for TM therapybecause it permits administration of lesser amounts of TM to achieveequivalent pharmacological effect compared to the native drug. Abiological and a half-life which is at least greater than a few minutesprovides for a more predictable therapeutic regimen.

In addition, these soluble thrombomodulin analogs can be producedeconomically and are easily purified and administered. A variety oftherapeutic uses are anticipated, particularly with respect toanticoagulant and/or antithrombotic therapies. In order to fullyappreciate the invention, the following detailed description is setforth.

I. Biological Activity of Thrombomodulin

The underlying pathology of thrombotic disorders is that a clot forms inresponse to a stimulus such as, for example, a damaged vessel wall. Thisstimulus triggers the coagulation cascade and thus generates thrombinwhich has the ability to convert fibrinogen to fibrin, the matrix of theclot. Thrombomodulin is an endothelial cell membrane protein that actsas a receptor for thrombin. In humans it is distributed on theendothelium of the blood vessels and lymphatics of all organs except thecentral nervous system. Thrombin has the ability to bind reversibly tothrombomodulin. When bound to thrombomodulin, thrombin is converted froma procoagulant enzyme to an anticoagulant enzyme. Thethrombin/thrombomodulin complex inhibits the coagulation cascade in atleast two distinct ways. First, thrombin's binding to thrombomodulinpotentiates thrombin-mediated activation of protein C. Activated proteinC inactivates other procoagulant components of the coagulation cascade,such as Factors Va and VIIIa, which in turn inhibits the conversion ofmore prothrombin to thrombin. Thrombin-mediated activation of protein Cis greatly enhanced when thrombin is bound to thrombomodulin, i.e., therate of protein C activation increases at least 1000-fold. Secondly,binding to thrombomodulin has direct anticoagulant effects such as theinhibition of thrombin-mediated conversion of fibrinogen to fibrin andthrombin-mediated activation and aggregation of platelets. Althoughnormally an integral component of the endothelial cell membrane,thrombomodulin can be released from the membrane in the presence ofsufficient detergent and retains the ability to bind to thrombin when insolution.

The preferred thrombomodulin analogs of this invention will protectagainst thrombus formation when administered systemically because theywill inhibit the generation of thrombin without disturbing othercoagulation parameters, e.g., the activation and aggregation ofplatelets. Thus the use of soluble thrombomodulin analogs will beeffective at preventing thrombus formation, yet is safer than nativethrombomodulin and other antithrombotics known in the art.

Diseases in which thrombus formation plays a significant etiologicalrole include myocardial infarction, disseminated intravascularcoagulation, deep vein thrombosis, pulmonary embolism, septic shock,acute respiratory distress syndrome, unstable angina, and other arterialor venous occlusive conditions. The thrombomodulin analogs of thisinvention are useful in all of these, as well as in other diseases inwhich thrombus formation is pathological. By useful it is meant that thecompounds are useful for treatment, either to prevent the disease or toprevent its progression to a more severe state. The compounds of thisinvention also provide a safe and effective anticoagulant, for example,in patients receiving bioprostheses, such as heart valves. Thesecompounds may replace heparin and warfarin in the treatment of, forexample, pulmonary embolism or acute myocardial infarction.

In particular these compounds would find a role in the prevention ofdeep vein thrombosis (DVT), for instance after surgery. The formation ofblood clots in the leg is itself a non-fatal condition but is veryclosely tied to the development of pulmonary embolism (PE), which isdifficult to diagnose and can be fatal. Despite the investigation andclinical use of several prophylactic regimens, DVT and the resulting PEremain a significant problem in many patient populations andparticularly in patients undergoing orthopedic surgery. Existingprophylactic treatments such as heparin, warfarin, and dextran typicallyreduce the incidence of DVT in orthopedic surgery patients from morethan 50% in patients at risk receiving no prophylaxis to 25-30% amongtreated patients. There are serious side effects, primarily bleedingcomplications. Currently, daily laboratory tests and adjustments indosage are required to minimize bleeding episodes while retaining someefficacy. Based on the shortcomings of existing prophylactics, anantithrombotic which is effective at preventing DVT without predisposingthe patient to bleeding could make a significant impact on patientrecovery and well-being.

Angioplasty is a procedure frequently used for restoring patency inoccluded arteries. Although patency may be restored, it is inherent inan angioplasty procedure that the endothelial lining of the artery isseverely damaged, and blood clots frequently begin to form. Solublethrombomodulin analogs administered in conjunction with angioplasty willprevent this deleterious side effect.

Many acute thrombotic and embolic diseases are currently treated withfibrinolytic therapy in order to remove the thrombus. The condition thathas been most investigated is acute myocardial infarction (heartattack). Agents currently in use for treating acute myocardialinfarction include streptokinase, tissue plasminogen activator, andurokinase. Use of these agents can lead to serious bleedingcomplications. Patients who have had a thrombus removed by fibrinolytictherapy and in whom the blood flow has been restored frequentlyreocclude the affected vessel, i.e., a clot reforms. Attempts have beenmade to prevent the reocclusions by increasing the dose or time oftreatment with a thrombolytic agent, but the incidence of bleeding thenincreases. Thus the therapeutic index for these drugs is narrow.

The use of thrombomodulin analogs provides protection againstreocclusion in parts because its action is local, i.e., where thrombinis being generated or being released from a clot. Therefore, when usedin combination with a thrombolytic agent whose dose can then bedecreased, the risk of bleeding can be substantially reduced.

Administration of single-chain thrombomodulin or TM analogs can beaccomplished by a bolus intravenous injection, by a constant intravenousinfusion, or by a combination of both routes. Also, solublethrombomodulin mixed with appropriate excipients may be taken into thecirculation from an intramuscular site. Systemic treatment withthrombomodulin analogs can be monitored by determining the activatedpartial thromboplastin time (APTT) on serial samples of blood taken fromthe patient. The coagulation time observed in this assay is prolongedwhen a sufficient level of thrombomodulin is achieved in thecirculation. However, this is a systemic measurement of efficacy, andthe inventors have discovered that an effective dose of soluble TManalog does not necessarily affect the APTT. As used herein, atherapeutically effective dose is defined as that level of TM analogsufficient to prevent formation of pathological clots. Dosing levels andregimens can be routinely adjusted by one of ordinary skill in the artso that an adequate concentration of thrombomodulin is maintained asmeasured by, for example, the activated partial thromboplastin clottingtime (APTT), the thrombin clotting time (TCT), or conversion of proteinC to activated protein C (APC) assays.

Several methods are known for the detection and monitoring of thromboticdisease. Deep venous thrombosis can be detected, for example, bycontrast venography, (Kerrigan, G. N. W., et al., (1974) British Journalof Hematology 26:469), Doppler ultrasound (Barnes, R. W. (1982) SurgeryClinics in North America 62:489-500), ¹²⁵ I-labeled fibrinogen uptakescanning (Kakkar, V. V., et al., (1972) Archives of Surgery 104:156,Kakkar, V. V., et al., (1970) Lancet i:540-542), impedanceplethysmography (Bynum, L. J. et al., (1978) Annals of Internal Medicine89:162), and thromboscintoscan (Ennis, J. T. and Elmes, R. J. (1977)Radiology 125:441). These methods are useful to monitor the efficacy ofthe methods and compositions described herein.

II. TM Analogs

A DNA sequence encoding the full-length native human thrombomodulinprotein has been isolated (European Patent Application No. 88870079.6,which is incorporated herein by reference). The cDNA sequence encodes a60.3 kDa protein of 575 amino acids, which includes a signal sequence ofabout 18 amino acids.

The sequences for bovine, mouse and human thrombomodulin exhibit a highdegree of homology with one another. By analogy with other proteins, thestructure of thrombomodulin can be presumptively divided into domains.The term "domain" refers to a discrete amino acid sequence that can beassociated with a particular function or characteristic. Typically, adomain exhibits a characteristic tertiary structural unit. Thefull-length thrombomodulin gene encodes a precursor peptide containingthe following domains:

    ______________________________________    Approximate Amino    Acid Position                Domain    ______________________________________    -18-1       Signal sequence     1-226      N-terminal domain (lectin domain; L)    227-462     6 EGF-like domains (E)    463-497     O-linked Glycosylation (D)    498-521     Stop Transfer Sequence (transmembrane domain)    522-557     Cytoplasmic domain    ______________________________________

See C. S. Yost et al., (1983) Cell, 34:759-766 and D. Wen et al., (1987)Biochemistry, 26:4350-4357, both incorporated herein by reference.

In the nomenclature used here, the subscript refers to the domainscontained in the TM analog: L=the lectin domain, E=the 6 EGF-likedomains, O=the O-linked glycosylation domain, M=the transmembranedomain, and C=the cytoplasmic domain. Thus, TM analog 6h/227-462,corresponds to a TM_(E) analog TME(Sf9) indicates that it is expressedin insect cells, TM_(LEO) (CHO) indicates that it is expressed in CHOcells, and TMD123 (Zushi, M., Gomi, K., Yamamoto, S., Maruyama, I.,Hayashi, T., and Suzuki, K. (1989) J. Biol. Chem. 264, 10351-10353) andTMD1 (Parkinson, J. F., Grinnell, B. W., Moore, R. E., Hoskins, J.,Vlahos, C. J., and Bang, N. U. (1990) J. Biol. Chem. 265, 12602-12610)correspond to TM_(LEO) analogs.

Particularly preferred single-chain TM analog compositions are thosethat have one or more of the following characteristics:

(i) they exhibit protease resistance,

(ii) they have homogeneous N- or C-termini,

(iii) they have been post-translationally modified, e.g., byglycosylation of at least some of the glycosylation sites of nativethrombomodulin,

(iv) they have linear double-reciprocal thrombin binding properties,

(v) they are soluble in aqueous solution in relatively low amounts ofdetergents and typically lack a stop transfer (transmembrane) sequence,

(vi) they retain activity after exposure to oxidants,

(vii) when bound to thrombin, they potentiate the thrombin-mediatedactivation of protein C but have a reduced ability to inhibit the directpro-coagulant activities of thrombin such as the conversion offibrinogen to fibrin or the activation and aggregation of platelets.

Assays for the last two characteristics can be run on an automaticcoagulation timer according to the manufacturer's specifications;Medical Laboratory Automation Inc. distributed by American ScientificProducts, McGaw Park, Ill. (See also H. H. Salem et al., (1984) J. Biol.Chem., 259:12246-12251, which is incorporated herein by reference). Incomparison to native thrombomodulin, preferred TM analogs have beenmodified to embrace the 6 epidermal growth factor EGF!-like domains andmay also contain the O-linked glycosylation and/or lectin domains.

In a preferred embodiment, soluble TM analogs are oxidation resistant.This refers to analogs that retain activity after exposure to oxidants.Such analogs are described in detail in co-pending co-assigned U.S.application Ser. No. 07/506,325, filed Apr. 9, 1990, incorporated hereinby reference.

For purposes of the present invention, the following terms are defined:

"Protease site" as used herein refers to an amino acid or series ofamino acids in a TM polypeptide which define a recognition, binding,cleavage, or other site susceptible to the activity of a protease, forexample, when one or more amino acid residues encompassed by this siteare substituted by another amino acid residue(s) or are deleted, theprotease is no longer able to cleave the TM at that site. This term alsoencompasses regions of the TM molecule which are inherently susceptibleto proteases, e.g., by being conformationally exposed and available to aprotease activity.

"Protease cleavage site" as used herein refers to the precise locationat which a protease cleaves the TM polypeptide analog.

"Single N-terminus" and "single C-terminus" are used herein to havetheir literal meanings which functionally refer to the property of thecomposition, e.g., wherein, upon conventional sequential amino acidsequence analysis, each degradation cycle results in the removal of anamino acid residue which is essentially devoid of a different amino acidresidue. Thus, after several cycles, e.g., 10 cycles, of stepwiseremoval of the N-terminal amino acids, essentially only one amino acidis recovered at each cycle. In particular, no more heterogeneity insequence is detected than would be statistically expected from acompletely pure single-chain polypeptide according to the analyticprocedure used.

"Single-chain TM" refers to a composition of TM which containssubstantially all uncleaved peptide chains. The polypeptides in asingle-chain composition need not all exhibit identical amino or carboxyterminal ends.

"Two-chain TM" refers to a composition containing physically detectableamounts, typically in excess of about 0.5-3%, of polypeptide which has abroken peptide bond.

"Devoid of two-chain thrombomodulin" as used herein means that thecomposition comprises essentially all single-chain TM. Typically, theamount of two-chain TM is less than about 25% by molar amount, moretypically less than 15%, preferably less than about 10%, more preferablyless than 5%, and in particularly preferred embodiments, less than 3%.Alternatively, the amount of two-chain TM in a composition is less thanthat which would cause a significant decrease in the specific activityof pure single-chain TM, e.g., the amount of two-chain TM is less thanthe amount which alters a linear double reciprocal plot defined herein.Thus, two-chain TM molecules are present in the form of a polypeptidechain having at least one scission which results in the production ofadditional N- and/or C-termini.

"Substantially retains the biological activity of native thrombomodulin"and similar terms, as used herein, means that the thrombomodulin sharesbiological activities with a native membrane bound TM molecule.Generally, the activity in units per milligram of protein is at leastabout 50%, ordinarily 75%, typically 85%, more typically 95%, preferably100% and more preferably over 100% of the activity of nativethrombomodulin. This biological activity can be that ofthrombin-mediated activation of protein C (APC), of activated partialthromboplastin clotting time (APTT), of thrombin clotting time (TCT), orof any of TM's biological, preferably therapeutic, activities. Thenative standard of comparison is a full-length membrane bound version ofTM, but in many cases, a soluble TM comprising the lectin/EGF/O-linkeddomain (TM_(LEO)) can be used as a more convenient standard.

"Glycosylation sites" refer to amino acid residues which are recognizedby a eukaryotic cell as locations for the attachment of sugar residues.The amino acids where sugars are attached are typically Asn (forN-linked sugars), threonine or serine (for O-linked sugars) residues.The specific site of attachment is typically signaled by a sequence ofamino acids, e.g., Asn-X-(Thr or Ser) for most N-linked attachment and(Thr or Ser)-X-X-Pro for most O-linked attachment, where X is any aminoacid. The recognition sequence for glycosaminoglycans (a specific typeof sulphated sugar) is generally Ser-Gly-X-Gly, but can also beX-Ser-Gly-X-Val. The terms N-linked and O-linked refer to the chemicalgroup that serves as the attachment site between the sugar moiety andthe amido acid residue. N-linked sugars are attached through an aminogroup; O-linked sugars are attached through an hydroxyl group.

"In vivo circulating half-life" refers to the average time it takes anadministered plasma activity in a mammal to decrease by one half.

"Native thrombomodulin" refers to the full length protein as it occursin nature. When biological activities are described with reference tothe native TM, the term embraces a detergent solubilized aqueous form.Often, in the context of comparison to an activity, a transfectedsoluble polypeptide may exhibit substantially identical properties.

"O-linked glycosylation domain" refers to the sequence of amino acidsnumbered from 463 through 485 of the native thrombomodulin sequence asdepicted in Table 1.

"Oxidation resistant analogs" refers to analogs of thrombomodulin whichare able to maintain a substantial amount of biological activity afterexposure to an oxidizing agent such as oxygen radicals, Chloramine T,hydrogen peroxide, or activated neutrophils.

"Pharmaceutical excipients" refers to non-toxic, medically-acceptablematerials which are used to complete a medical therapeutic. Thesematerials can be inert, such as water and salt, or biologically active,such as an antibiotic or analgesic.

"Reduced ability" refers to a statistically meaningful lowering of abiological property. The property is unlimited and the measurement orquantification of the property is by standard means.

"Sugar residues" refers to hexose and pentose carbohydrates includingglucosamines and other carbohydrate derivatives and moieties which arecovalently linked to a protein.

"Sulfate substituents" are sulfur-containing substituents on pentose orhexose sugars.

"Thrombin-mediated conversion of fibrinogen to fibrin" refers to theenzymatic activity by which thrombin cleaves the precursor proteinfibrinogen to make fibrin monomer, which subsequently polymerizes toform a blood clot.

"Thrombotic disease" refers to a pathogenic condition in a mammalcharacterized by the formation of one or more thrombi that are or can bedetrimental to the health of the mammal.

"Thrombomodulin analogs" are peptides which substantially retain thebiological activity of natural TM, as discussed above, and which have amolecular structure different from that of a natural version TM. Forexample, the term refers to proteins having an amino acid sequenceidentical or homologous with that of native thrombomodulin, to insolubleand soluble thrombomodulin peptides or fragments, and to oxidationresistant TM species, all having thrombomodulin-like activity. Thesecompounds also include derivatives and molecules comprising amino acidchanges which do not significantly decrease the protein C activationcofactor properties of the protein when compared with native TM.

"Transfer vector" refers to a vector cotransfected into another cell,e.g., an insect cell, with, e.g., a wild-type baculovirus. The transfervector is constructed in such a way as to encourage a recombinationbetween a viral, e.g., the baculovirus, genome and the transfer vector,e.g., replacing the baculovirus polyhedron gene with a heterologoustarget gene. Where a vector is being maintained by a host cell, thevector may either be stably replicated by the cells during mitosis as anautonomous structure, or is incorporated within the host's genome.

As used herein, a "soluble TM analog" is a TM analog which is soluble inan aqueous solution, and typically can be secreted by a cell. Forpharmacological administration, the soluble TM analog or an insolubleanalog comprising the native cytoplasmic domain, or analog mayoptionally be combined with phospholipid vesicles, detergents, or othersimilar compounds well known to those skilled in the art ofpharmacological formulation. The preferred TM analogs of the presentinvention are soluble in the blood stream, making the analogs useful invarious anticoagulant and other therapies. These modifications typicallydo not significantly affect many activities relative to nativethrombomodulin, e.g., affinity for thrombin or activity in protein Cactivation.

Two preferred analogs encompass the 6 EGF-like domains and are4t/227-462 where the analog has the last four residues of the humantissue plasminogen activator signal peptide and 6h/227-462 where the 6hrepresents the last six residues of the hypodermin A signal sequence.More preferred are these analogs rendered oxidation resistant bysubstitution of the methionine at position 388 with leucine.

Another preferred embodiment is an analog corresponding to amino acids3-490, with modifications to Met388, Arg456, His457, Ser474, anddeletions at the N-and C-termini. This embodiment is particularly usefulwhen expressing the gene in eukaryotic cells, e.g., in animal cells,vertebrate cells, insect cells, mammalian cells, human cells, etc., inparticular, CHO and CHL1 cells.

A. General Methods for Making TM Analoqs

This invention embraces molecular genetic manipulations that can beachieved in a variety of known ways. The recombinant cells, plasmids,and DNA sequences of the present invention provide a means to producepharmaceutically useful compounds wherein the compound, secreted fromrecombinant cells, is a soluble derivative of thrombomodulin.

Generally, the definitions of nomenclature and descriptions of generallaboratory procedures used in this application can be found in J.Sambrook et al., Molecular Cloning, A Laboratory Manual, (1989) ColdSpring Harbor Laboratory, Cold Spring Harbor, N.Y. The manual ishereinafter referred to as Sambrook and is hereby incorporated byreference. In addition, Ausubel et al., eds., Current Protocols inMolecular Biology, (1987 and periodic updates) Greene PublishingAssociates, Wiley-Interscience, New York, discloses methods useful inthe present application.

All enzymes are used according to the manufacturer's instructions.

Oligonucleotides that are not commercially available can be chemicallysynthesized according to the solid phase phosphoramidite triester methodfirst described by S. L. Beaucage and M. H. Caruthers, (1981)Tetrahedron Letts., 22(20):1859-1862 using an automated synthesizer, asdescribed in D. R. Needham-VanDevanter et al., (1984) Nucleic AcidsRes., 12:6159-6168. Purification of oligonucleotides was by eithernative acrylamide gel electrophoresis or by anion-exchange HPLC asdescribed in Pearson, J. D., and Regnier, F. E. (1983) J. Chrom.,255:137-149. Nucleotide sizes are given in either kilobases (kb) or basepairs (bp). These are estimates derived from agarose or acrylamide gelelectrophoresis or from published DNA sequences.

The sequence of the cloned genes and synthetic oligonucleotides can beverified using the chemical degradation method of Maxam, A. M., et al.,(1980) Methods in Enzymology, 65:499-560, or similar methods. Thesequence can be confirmed after the assembly of the oligonucleotidefragments into the double-stranded DNA sequence using the method ofMaxam and Gilbert, supra, or the chain termination method for sequencingdouble-stranded templates of Wallace, R. B., et al., (1981) Gene,16:21-26. Southern Blot hybridization techniques were carried outaccording to Southern et al., (1975) J. Mol. Biol., 98:503.

Embodiments of this invention often involve the creation of novelpeptides and genes by in vitro mutagenesis. Target genes are isolated inintermediate vectors and cloned for amplification in prokaryotes such asE. coli, Bacillus, or Streptomyces. Most preferred is E. coli becausethat organism is easy to culture and more fully understood than otherspecies of prokaryotes. The Sambrook manual contains methodologysufficient to conduct all subsequently described clonings in E. coli.Strain MH-1 is preferred unless otherwise stated. All E. coli strainsare grown on Luria broth (LB) with glucose, or M9 medium supplementedwith glucose and acid-hydrolyzed casein amino acids. Strains withresistance to antibiotics were maintained at the drug concentrationsdescribed in Sambrook. Transformations were performed according to themethod described by Morrison, D.A. (1977) J. Bact., 132:349-351 or byClark-Curtiss, J. E., and Curtiss, R. (1983) Methods in Enzymology,101:347-362, Eds. R. Wu et al., Academic Press, New York. Representativevectors include pBR322 and the pUC series which are available fromcommercial sources.

B. Gene Synthesis

The gene encoding native thrombomodulin has been isolated and sequencedfrom several species, both in its genomic form and as a cDNA (Jackman,R., et al., (1986) Proc. Natl. Acad. Sci. USA. 83:8834-8838 and (1987)84:6425-6429, both of which are herein incorporated by reference).

Publication of the full length DNA sequence encoding humanthrombomodulin and thrombin facilitates the preparation of genes and isused as a starting point to construct DNA sequences encoding TMpeptides. See, e.g., Genbank Register c/o IntelliGenetics, Inc.,Mountain View, Calif. The peptides of the present invention arepreferably soluble derivatives which lack the stop transfer sequence ofTM in addition to having internal amino acid substitutions. Furthermore,these analogs are secreted from eukaryotic cells which have beentransfected or transformed with plasmids containing genes which encodethese polypeptides. Methods for making modifications, such as amino acidsubstitutions, deletions, or the addition of signal sequences to clonedgenes are known. Specific methods used herein are described below.

The full-length gene for thrombomodulin can be prepared by severalmethods. Human genomic libraries are commercially available.Oligonucleotide probes, specific to these genes, can be synthesizedusing the published gene sequence. Methods for screening genomiclibraries with oligonucleotide probes are known. The publication of thegene sequence for thrombomodulin demonstrates that there are no intronswithin the coding region. Thus a genomic clone provides the necessarystarting material to construct an expression plasmid for thrombomodulinusing known methods.

A thrombomodulin encoding DNA fragment can be retrieved by takingadvantage of restriction endonuclease sites which have been identifiedin regions which flank or are internal to the gene. (Jackman, R. W., etal., (1987) Proc. Natl. Acad. Sci. USA., 84:6425-6429).

Alternatively, the full length genes can also be obtained from a cDNAlibrary. For example, messenger RNA prepared from endothelial cellsprovides suitable starting material for the preparation of cDNA. A cDNAmolecule containing the gene encoding thrombomodulin is identified asdescribed above. Methods for making cDNA library are well known (SeeSambrook, supra).

Genes encoding TM peptides may be made from wild-type TM genes firstconstructed using the gene encoding full length thrombomodulin. Apreferred method for producing wild-type TM peptide genes for subsequentmutation combines the use of synthetic oligonucleotide primers withpolymerase extension on a mRNA or DNA template. This polymerase chainreaction (PCR) method amplifies the desired nucleotide sequence. U.S.Pat. Nos. 4,683,195 and 4,683,202 describe this method. Restrictionendonuclease sites can be incorporated into the primers. Genes amplifiedby the PCR reaction can be purified from agarose gels and cloned into anappropriate vector. Alterations in the natural gene sequence can beintroduced by the techniques of in vitro mutagenesis or by use of thepolymerase chain reaction with primers that have been designed toincorporate appropriate mutations. See Innis, M. et al., eds. (1990),PCR Protocols: A Guide to Methods and Applications, Academic Press.

The TM peptides described herein are typically secreted when expressedin eukaryotic cell culture. Secretion may be obtained by the use of thenative signal sequence of the thrombomodulin gene. Alternatively, genesencoding the TM peptides of the present invention may be ligated inproper reading frame to a signal sequence other than that correspondingto the native thrombomodulin gene. For example, the signal sequence oft-PA, (see WO 89/00605 incorporated herein by reference) or ofhypodermin A or B (see EP 326,419 which is incorporated hereby byreference) can be linked to the polypeptide (See Table 2). In onepreferred embodiment of the present invention, use is made of the signalsequence of t-PA which contains the second intron of the human t-PAgene. The inclusion of the intron enhances the expression level of theadjacent structural gene.

With some analogs of this invention, those portions of the gene encodingthe stop transfer and cytoplasmic domains of the carboxyl terminalregion of the native thrombomodulin gene are deleted. Therefore, it isnecessary to add a stop codon so that translation will be terminated atthe desired position. Alternatively, a stop codon can be provided by thedesired expression plasmid. Additionally, a polyadenylation sequence canbe utilized to ensure proper processing of the mRNA in eukaryotic cellsencoding the TM analog. Also, it may be useful to provide an initiationcodon, if one is not present, for expression of the TM peptides. Suchsequences may be provided from the native gene or by the expressionplasmid.

Cloning vectors suitable for replication and integration in prokaryotesor eukaryotes and containing transcription and translation terminators,initiation sequences, and promoters useful for regulation of theexpression of TM peptides are described herein. The vectors arecomprised of expression cassettes containing at least one independentterminator sequence, sequences permitting replication of the plasmid inboth eukaryotes and prokaryotes, i.e., shuttle vectors, and selectionmarkers for both prokaryotic and eukaryotic systems.

C. Expression of TM Peptides in Prokaryotic Cells

In addition to the use of cloning methods in E. coli for amplificationof cloned nucleic acid sequences it may be desirable to express TManalogs in prokaryotes. As discussed in greater detail below, thecarbohydrate moieties of the mature protein are not essential foractivity as a cofactor for the activation of protein C but do have aneffect on the direct anticoagulant properties of the TM analogs as wellas the molecule's half-life in circulation. Expression of thrombomodulinanalogs in E. coli has provided a useful tool for analysis of thisissue. It is possible to recover a therapeutically functional proteinfrom E. coli transformed with an expression plasmid encoding a solubleTM analog.

Methods for the expression of cloned genes in bacteria are well known.To obtain high level expression of a cloned gene in a prokaryoticsystem, it is often essential to construct expression vectors whichcontain, at the minimum, a strong promoter to direct mRNA transcriptiontermination. Examples of regulatory regions suitable for this purposeare the promoter and operator region of the E. coli β-galactosidasegene, the E. coli tryptophan biosynthetic pathway, or the leftwardpromoter from the phage lambda. The inclusion of selection markers inDNA vectors transformed in E. coli are useful. Examples of such markersinclude the genes specifying resistance to ampicillin, tetracycline, orchloramphenicol.

See Sambrook, supra, for details concerning selection markers andpromoters for use in E. coli. In one described embodiment of thisinvention, pUC19 is used as a vector for the subcloning andamplification of desired gene sequences.

D. Expression of TM Peptides in Eukaryotic Cells

It is expected that those of skill in the art are knowledgeable in theexpression systems chosen for expression of the desired TM peptides andno attempt to describe in detail the various methods known for theexpression of proteins in eukaryotes will be made.

The DNA sequence encoding a soluble TM analog can be ligated to variousexpression vectors for use in transforming host cell cultures. Thevectors typically contain marker genes and gene sequences to initiatetranscription and translation of the heterologous gene.

The vectors preferably contain a marker gene to provide a phenotypictrait for selection of transformed host cells such as dihydrofolatereductase, metallothionein, hygromycin, or neomycin phosphotransferase.The nuclear polyhedral viral protein from Autographa californica isuseful to screen transfected insect cell lines from Spodopterafrugiperda and Bombyx mori to identify recombinants. For yeast, Leu-2,Ura-3, Trp-1, and His-3 are known selectable markers (Gene (1979)8:17-24). There are numerous other markers, both known and unknown,which embody the above scientific principles, all of which would beuseful as markers to detect those eukaryotic cells transfected with thevectors embraced by this invention.

Of the higher eukaryotic cell systems useful for the expression of TManalogs, there are numerous cell systems to select from. Illustrativeexamples of mammalian cell lines include RPMI 7932, VERO, and HeLacells, Chinese hamster ovary (CHO) cell lines, WI38, BHK, COS-7, C127,or MDCK cell lines. A preferred mammalian cell line is CHL-1 or CHO.When CHL-1 is used, hygromycin is included as a eukaryotic selectionmarker. CHL-1 cells are derived from RPMI 7932 melanoma cells, a readilyavailable human cell line. The CHL-1 cell line has been deposited withthe ATCC according to the conditions of the Budapest Treaty and has beenassigned #CRL 9446, deposited Jun. 18, 1987. Cells suitable for use inthis invention are commercially available from the American Type CultureCollection. Illustrative insect cell lines include Spodoptera frugiperda(fall Armyworm) and Bombyx mori (silkworm).

As indicated above, the expression vector, e.g., plasmid, which is usedto transform the host cell, preferably contains gene sequences toinitiate the transcription, and sequences to control the translation ofthe TM peptide gene sequence. These sequences are referred to asexpression control sequences. When the host cell is of insect ormammalian origin, illustrative expression control sequences include butare not limited to the following: the retroviral long terminal repeatpromoters ((1982) Nature, 297:479-483), SV40 promoter ((1983) Science,222:524-527, thymidine kinase promoter (Banerji, J., et al., (1982)Cell, 27:299-308), or the beta-globin promoter (Luciw, P. A., et al.,(1983) Cell, 33:705-716). The recipient vector nucleic acid containingthe expression control sequences is cleaved using restriction enzymesand adjusted in size as necessary or desirable. This segment is ligatedto a DNA sequence encoding a TM peptide by means well known in the art.

When higher animal host cells are employed, polyadenylation ortranscription termination sequences normally need to be incorporatedinto the vector. An example of a polyadenylation sequence is thepolyadenylation sequence from SV40, which may also function as atranscription terminator.

Genes incorporated into the appropriate vectors can be used to directsynthesis of proteins in either transient expression systems or instable clones. In the former case yields are low, but the experimentsare quick. In the latter case it takes more time to isolate highproducing clones. Different vectors may be used for the two differenttypes of experiments. In particular, in the case of transientexpression, sequences may be included within the plasmid that allow theplasmid to replicate to a high copy number within the cell. Thesesequences may be derived from a virus such as SV40 (e.g., Doyle, C. etal., (1985) J. Cell Biol., 100:704-714) or from chromosomal replicatingsequences such as murine autonomous replicating sequences (Weidle etal., (1988) Gene, 73:427-437). The vector for use in transientexpression will also often contain a strong promoter such as the SV40early promoter (e.g., van Zonnenfeld, A. et al., (1987) Proc. Natl.Acad. Sci. USA., 83:4670-4674) to control transcription of the gene ofinterest. While transient expression provides a rapid method for assayof gene products, the plasmid DNA is not incorporated into the host cellchromosome. Thus, use of transient expression vectors does not providestable transfected cell lines. A description of a plasmid suitable fortransient expression is provided by Aruffo, A., and Seed, B. (1987)Proc. Natl. Acad. Sci. USA., 84:8573-8577.

TM analogs may alternatively be produced in the insect cell linesdescribed above using the baculovirus system. This system has beendescribed by Luckow, V. A., and Summers, M. D. (1988) Bio/Technology,6:47-55. Generally, this expression system provides for a level ofexpression higher than that provided by most mammalian systems. Thebaculovirus infects the host insect cells, replicates its genome throughnumerous cycles, and then produces large amounts of polyhedron crystals.The polyhedron gene can be replaced with a TM peptide gene. Thepolyhedron promoter will then make large amounts of analog proteinfollowing infection of the culture host cell and replication of thebaculovirus genome. The non-secreted gene product is harvested from thehost 3-7 days post infection. Alternatively, the TM peptide may besecreted from the cells if appropriate signal sequences are present onthe protein. The host cells are competent or rendered competent fortransfection by various means. There are several well-known methods ofintroducing DNA into animal cells. These include: calcium phosphateprecipitation, DEAE-dextran technique, fusion of the recipient cellswith bacterial protoplasts containing the DNA, treatment of therecipient cells with liposomes containing the DNA, electroporation, andmicroinjection of the DNA directly into the cells. See, Perbal, B."Practical Guide to Molecular Cloning," 2nd edition, John Wiley & Sons,New York and Wigler, et al., (1987) Cell, 16:777-785, which are eachincorporated herein by reference.

E. Culturing Cells

It is preferred that the host cell is capable of rapid cell culture andable to appropriately glycosylate expressed gene products. Cells knownto be suitable for dense growth in tissue culture are particularlydesirable and a variety of invertebrate or vertebrate cells, both normaland transformed, have been employed in the art, In particular, cellswhich are suitable hosts for recombinant TM expression and which produceor contain, under culturing conditions, a protease which results in thecleavage of native thrombomodulin now pose no problem in cleaving themutated protease insensitive TM analog. Examples of such cells includeCHO, CHL-1 (characterized as a human melanoma cell), Sf9 cells, etc.,which are publicly available from the ATCC.

The transfected cells are grown up by means well known in the art. Forexamples, see Kuchler et al. (1977) Biochemical Methods in Cell Cultureand Virology, The expression products are harvested from the cell mediumin those systems where the protein is secreted from the host cell orfrom the cell suspension after disruption of the host cell system by,e.g., mechanical or enzymatic means, which are well known in the art.

F. Purification of TM Analogs

It is preferred that the TM peptides of this invention be secreted bycultured recombinant eukaryotic cells. The TM analogs are produced inserum-free or serum supplemented media and are secreted intact. Ifprokaryotic cells are used, the TM analogs may be depositedintracellularly. The peptides may be fully or partially glycosylated ornon-glycosylated. Following the growth of the recombinant cells andconcomitant secretion of TM analogs into the culture media, this"conditioned media" is harvested. The conditioned media is thenclarified by centrifugation or filtration to remove cells and celldebris. The proteins contained in the clarified media are concentratedby adsorption to any suitable resin such as, for example, Q Sepharose ormetal chelators, or by use of ammonium sulfate fractionation,polyethylene glycol precipitation, or by ultrafiltration. Other meansknown in the art may be equally suitable. Further purification of the TManalogs can be accomplished in the manner described in Galvin, J. B., etal., (1987) J. Biol. Chem., 262:2199-2205 and Salem, H. H. et al.,(1984) J. Biol. Chem., 259:12246-12251 and in the manner described inthe embodiment disclosed herein. The purification of TM analogs secretedby cultured cells may require the additional use of, for example,affinity chromatography, ion exchange chromatography, sizingchromatography, or other conventional protein purification techniques.See, e.g., Deutscher (ed.), "Guide to Protein Purification" in Methodsin Enzymology, Vol. 182 (1990).

Recombinant TM analogs may be found in different forms which aredistinguishable under nonreducing chromatographic conditions. Removal ofthose species having a low specific activity is desirable and isachieved by a variety of chromatographic techniques including anionexchange or size exclusion chromatography. Recombinant TM analogs may beconcentrated by pressure dialysis and buffer exchanged directly intovolatile buffers (e.g., N-ethylmorpholine (NEM), ammonium bicarbonate,ammonium acetate, and pyridine acetate). In addition, samples can bedirectly freeze-dried from such volatile buffers resulting in a stableprotein powder devoid of salt and detergents. In addition, freeze-driedsamples of recombinant analogs can be efficiently resolubilized beforeuse in buffers compatible with infusion (e.g., phosphate bufferedsaline). Other suitable salts or buffers might include hydrochloride,hydrobromide, sulfate acetate, benzoate, malate, citrate, glycine,glutamate, and aspartate.

G. Oxidation Resistant TM analogs

Native thrombomodulin is susceptible to oxidation and when oxidizedloses its ability to promote the activation of protein C. Many of thedisease conditions requiring anticoagulation are also associated withhigh levels of toxic oxygen radicals, which can inactivate biomoleculesand cause significant tissue damage. Examples of these conditions arereperfusion injury associated with myocardial infarction, DIC associatedwith septicemia, and alveolar fibrosis associated with adult respiratorydistress syndrome. (See, Otani, H., et al., (1984) Circ. Res.55:168-175, Saldeen, T., (1983) Surg. Clin. N.A. 63(2):285-304, andIdell, S., et al., (1989) J. Clin. Inv. 84:695-705.) In addition, anywound, such as occurring in surgical procedures, involves the influx ofactivated monocytes, polymorphonuclear leukocytes, etc., which cancreate toxic oxygen species as well as releasing a host of proteolyticenzymes, such as elastase. The connection between endothelial celldamage, inflammation, and thrombosis has long been recognized (see TheMolecular and Cellular Biology of Wound Repair, ed. Clark, R. A. F. andP. M. Henson (1988), for example). Thrombomodulin is subject toinactivation by exposure to toxic oxygen species and this is expected tohave a significant role in many pathogenic states.

Methods for rendering amino acids, specifically methionines, resistantto oxidation are well known in the art. It is possible to chemicallymodify thiol ether groups with iodoacetic acid, for example, to formoxidation resistant sulphonium groups (Gundlach, H. G., et al., (1959)J. Biol. Chem. 234:1754). A preferred method is by removing thesusceptible amino acid or replacing it with one or more different aminoacids that will not react with oxidants. The amino acids leucine,alanine, and glutamine would be particularly preferred amino acidsbecause of their size and neutral character. Four methionines of solublethrombomodulin may be subject to oxidation, particularly those locatedat residues 291 and 388. If only one methionine is to be blocked oreliminated, it is preferred that it be the residue at position 388.

Methods by which amino acids can be removed or replaced in the sequenceof a protein are well known. See, e.g., Sambrook et al., supra; Ausubelet al., supra; U.S. Pat. No. 4,737,462; U.S. Pat. No. 4,588,585; EP-0285123; and references cited therein. Genes that encode a peptide with analtered amino acid sequence can be made synthetically, for example. Apreferred method is the use of site-directed in vitro mutagenesis.Site-directed mutagenesis involves the use of a syntheticoligodeoxyribonucleotide containing a desired nucleotide substitution,insertion, or deletion designed to specifically alter the nucleotidesequence of a single-strand target DNA. Hybridization of thisoligonucleotide, also called a primer, to the single-strand template andsubsequent primer extension produces a heteroduplex DNA which, whenreplicated in a transformed cell, will encode a protein sequence withthe desired mutation.

To determine the resistance to loss of thrombomodulin activity due tooxidation, the test material (100-250 μg/ml) is first incubated with anoxidant such as, for example, chloramine-T, hydrogen peroxide at 5-10 mMchloramine-T, or 200-1000 mM hydrogen peroxide in a buffer of 0.2%N-ethylmorpholine and 0.008% Tween 80 at pH 7.0, for 20 minutes at roomtemperature. A buffer of PBS with 0.1% BSA may also be used. After suchoxidant exposure, the test material is evaluated using one of thebioactivity assays, e.g., that described below specifically for theability to act as a cofactor for the activation of protein C. Thosemutant TM analogs that retain at least 60%, ordinarily 70%, morenormally 80%, and preferably 90%, of activity they had prior to exposureto oxidants are considered to be oxidation resistant as compared to awild-type (non-mutant) TM analog or native thrombomodulin.

H. Laboratory Assays for Measuring TM Activity

A number of laboratory assays for measuring TM activity are available.Protein C cofactor activity can be measured in the assay described bySalem, et al., (1984) J. Biol. Chem. 259(19):12246-12251 and Galvin, etal., (1987) J. Biol. Chem. 262(5):2199-2205. In brief, this assayconsists of two steps. The first is the incubation of the test TM analogwith thrombin and protein C under defined conditions (see Examplesbelow). In the second step, the thrombin is inactivated with hirudin orantithrombin III and heparin, and the activity of the newly activatedprotein C is determined by the use of a chromogenic substrate, wherebythe chromophore is released by the proteolytic activity of activatedprotein C. This assay is carried out with purified reagents.

Alternatively the effect of a TM analog can be measured using plasma inclotting time assays such as the activated partial thromboplastin time(APTT), thrombin clotting time (TCT), and/or prothrombin time (PT). TheAPTT assay is dependent on both the activating of protein C, as well asthe direct inhibition of thrombin, while the TCT and PT assays aredependent only on the inhibition of thrombin. Prolongation of theclotting time in any one of these assays demonstrates that the moleculecan inhibit coagulation in plasma.

The above assays are used to identify soluble TM analogs that are ableto bind thrombin and to activate protein C in both purified systems andin a plasma milieu. Further assays are then used to evaluate otheractivities of native thrombomodulin such as inhibition of thrombincatalyzed formation of fibrin from fibrinogen (Jakubowski, et al.,(1986) J. Biol. Chem. 261(8):3876-3882), inhibition of thrombinactivation of Factor V (Esmon, et al., (1982) J. Biol. Chem.257:7944-7947), accelerated inhibition of thrombin by antithrombin IIIand heparin cofactor II (Esmon, et al., (1983) J. Biol. Chem.258:12238-12242), inhibition of thrombin activation of Factor XIII(Polgar, et al., (1987) Thromb. Haemostas. 58:140), inhibition ofthrombin mediated inactivation of protein S (Thompson and Salem, (1986)J. Clin. Inv. 78(1):13-17) and inhibition of thrombin mediated plateletactivation and aggregation (Esmon, et al., (1983) J. Biol. Chem.258:12238-12242).

In the present invention, the TM analogs do not necessarily have allactivities equal to that of native thrombomodulin. For example, if onecompares an amount of a TM analog of the present invention with anequivalent amount of native chondroitin sulfonated membrane boundthrombomodulin (as measured in units of protein C cofactor activity,defined below) the TM analog will usually have at least a 20% reduction,and preferably a 50% reduction in its ability to inhibitthrombin-mediated conversion of fibrinogen to fibrin compared to thenative thrombomodulin.

I. Methods for Altering the Glycosylation of TM Analogs

Carbohydrate substituents on proteins can affect both biologicalactivity and circulating half-life. In order to make some TM analogs ofthe present invention, O-linked glycosaminoglycan carbohydrate such asis found in the native thrombomodulin protein, should be eliminated.There are numerous ways of accomplishing this objective. One methodwould be the treatment of the O-linked carbohydrate containing proteinwith a glycohydrolase known to specifically degrade sulfatedglycosaminoglycans, such as chondroitinase ABC or hyaluronidase. Thismethod is described in Bourin, M. et al., (1988) J. Biol. Chem.263(17):8044-8052, which is herein incorporated by reference.

A second method for eliminating the O-linked carbohydrate is byintroducing site directed mutations into the protein. The attachment ofglycosaminoglycans is typically directed by a consensus recognitionsequence of amino acids X-serine-glycine-X-glycine-X (Bourdon, M. A., etal., (1987) Proc. Natl. Acad. Sci. USA. 84:3194-3198) where X is anyamino acid. The recognition sequence for other types of O-linked sugarsis generally threonine/serine-X-X-proline. The O-linked domain ofnatural thrombomodulin normally has at least one potentialglycosaminoglycan addition site (aa 472 and/or 474), and four otherpotential O-linked carbohydrate addition sites (aa 464, 472, 474, 480and 486), depending upon the cell type. Any change introduced into thenucleotide sequence that removes or changes the identity of any one ormore of the amino acids in this recognition sequence might eliminate thepotential O-linked carbohydrate attachment site. Methods of introducingsite directed mutations into a nucleotide sequence are described above.For example, one or more of these serine or threonine residues may bemodified to an unglycosylatable amino acid, e.g., alanine.

A preferred method of eliminating O-linked carbohydrate from a TM analogis by making an analog peptide that does not include the amino acidsthat are considered to be the O-linked domain, i.e., amino acids 468through 485 of the native thrombomodulin gene sequence as shown inTable 1. Methods of accomplishing this are well known in the art andhave been described above.

The circulating half-life of a protein can be altered by the amount andcomposition of carbohydrate attached to it. The TM analogs of thepresent invention contain both O-linked and N-linked carbohydrate. Inaddition to the potential O-glycosylation sites discussed above thereare potential N-linked sites, e.g., at amino acids 29, 97, 98, 364, 391and 393 and potential O-linked sites, e.g., at amino acids 319, 393 and396. Methods of altering carbohydrate composition in addition to thosedescribed above are: 1) expression of the TM analog gene in bacteriasuch E. coli, which does not have the cellular mechanisms necessary toglycosylate mammalian proteins, 2) expression of the TM analog gene invarious eukaryotic cells, as each has its own characteristic enzymesthat are responsible for the addition of characteristic sugar residues,and 3) treatment with chemicals such as hydrofluoric acid. Hydrofluoricacid, for example, chemically digests acidic and neutral sugars whileleaving intact sugars such as N-acetyl glucosamines and, under certainconditions, galactosamines.

J. Protease Resistant Analogs

As noted above, when recombinantly produced TM is expressed in culture,especially in eukaryotic cells, e.g., CHO cells, the TMs containsubstantial amounts of a two-chain version. This is detectable, e.g., bya binding property profile which indicates that there is a species witha different binding constant present, due to cleavage of theheterologous protein by an endopeptidase present under culturingconditions or during the purification process. This endopeptidase may bea constituent of, e.g., the host cell, a microbiological contaminant,the culture medium, etc. Analysis on SDS-PAGE under reducing conditionsreveals that, when TM analogs are prepared in CHO cells and isolatedfrom the conditioned media as disclosed herein, a protein bandcorresponding to a molecular weight of about 80 kD is present inaddition to the 94 kD protein band which corresponds to single-chainsoluble TM analog, as determined using rabbit polyclonal antibodies toinsect cell 6EGF, e.g., TME (S9), or stained gels. However, the samematerial expressed in CHL-1 cells apparently has less of this degradedmaterial. This indicates that the extent of proteolytic activity is maybe cell-line dependent.

A unique protease cleavage site in the human thrombomodulinextracellular domain has now been identified in various human analogs.In addition to the expected heterogeneity in the N-terminus (bothFPAPAEP and APAEP N-termini are found) caused by signal sequencecleavage heterogeneity. These analogs contain a new sequence ₋₋ IGTD₋₋D₋₋ K, which is consistent with proteolysis of single-chain TM betweenArg⁴⁵⁶ and His⁴⁵⁷. The amount of protein present in this cleaved form isas high as 50% of the TM chains.

This proteolytic cleavage site is formed in the last (c) loop of thesixth EGF domain, and thus the protein fragment is covalently heldtogether by the last disulfide bond in the loop. This is furthersupported by the fact that the two bands are only seen on reducing gels.The 80 kDa band is the N-terminal fragment, based upon size andimmunoreactivity. Therefore, TM analogs expressed in CHO cells, as wellas in other cell lines which possess similar proteases that degrade theTM analog, are contaminated with cleaved two-chain material thatexhibits similar molecular properties, e.g., molecular weight and aminoacid sequence when assayed under the same conditions. Therefore,purification properties will often be similar, even though the TM analogis cleaved into a two-chain version, which is held together by disulfidebond(s).

As was noted, TMS cleavage site occurs in the c loop of the 6EGF domainof TM. Deletion of this loop in various constructs was shown to resultin substantial loss in thrombin binding, evidenced by a large (˜7-fold)increase in K_(d) for thrombomodulin. Therefore, the contaminatingtwo-chain material likely results in a similar loss of specific activityof such preparations. Furthermore, since other binding sites on themolecule are intact, the two-chain material should act as a competitiveinhibitor of the single-chain TM analog. It is very difficult toseparate two-chain material from the intact one-chain species, so it isimportant to produce highly homogeneous, intact single-chain TM which isnot subject to proteolytic cleavage. This result has been accomplishedthrough the construction of TM analogs, as disclosed herein, whichremove and/or replace proteolytic cleavage sites and thus solve thisheretofore unappreciated problem. The present invention allows forproviding both full-length membrane-associated or soluble TM analogswhich are resistant to cleavage by said protease(S).

Mutations can be routinely introduced into the TM analogs to modify theprotease cleavage site in accordance with the procedures describedherein. However, the c loop of 6EGF has been shown to be important inthrombin binding, and it is important that the binding properties ofthis area be maintained in the analog produced. The biological activityof the thus-obtained molecule would be maintained, or an increase inoverall activity of a TM analog composition achieved, by preventingproteolysis. This will avoid loss of activity caused by change in thestructure of the initial domain thought to be important in binding TM tothrombin. For example, since in rabbits, mice, and cows the 456-457sequence of TM is Gly-Gln instead of Arg-His, as in the human TM, thismodification is of particular interest. Other, similar, site specificmutations can be employed to routinely identify a modified sequencewhich is not subject to proteolysis, yet maintains the desired level ofbiological activity. For example, by homology to other similar EGF-likeproteins, it can be seen that this region of the molecule is most likelyto be in a β-sheet structure between reverse turns around Pro⁴⁵⁰ /Asp⁴⁵¹and Thr⁴⁶⁰ /Asp⁴⁶¹. By this analysis, especially favorable substitutionswould be those which incorporate amino acids found in high frequency inβ-sheet structures, e.g., His, Val, Ile, Phe, Tyr, Trp, and Thr. Otherfavorable substitutions would be those which incorporate amino acidsless likely to be found in β-sheet structures, e.g., Cys, Glu, Lys, Asp,Asn, and Pro. Certain other residues include, e.g., Cys, to preventincorrect disulfide bonding with the other, structurally important,cysteines; Pro, which is less consistent with a β-sheet structure; andLys and Arg, which may incorporate alternative, protease cleavage sites.Thus, one of ordinary skill in the art can easily and routinelydetermine the structure of TM analogs which will be resistant toprotease cleavage, at this site or any other protease cleavage site. Allsuch structures meeting the requirements described herein are includedas part of this invention.

Of course, this modification can be employed in addition to one or moreof the other modifications disclosed herein, e.g., for introducingoxidation resistance, increasing half-life of the analog in serum byremoving glycosylation sites, homogeneous amino termini, homogeneouscarboxy termini, etc., to provide a molecule having improvedcharacteristics at several sites.

In addition to the previously described modifications, single-chain TMcan be provided by removal of two-chain TM from preparations whichcontain it by routine protein purification methods.

K. Production of Thrombomodulin Analogs Having a Unique N-terminus

In addition to the above problem of preventing the production of TMpolypeptide compositions exhibiting more than one N-terminus due tointernal endoproteolytic cleavage, native thrombomodulin has anadditional inherent heterogeneity at the normal N-terminus due toimprecise processing of the signal sequence. One characteristic ofpurity used in the definition of protein purity, e.g., in particular forregulatory approval for in vivo administration, is the detection of asingle unique N-terminal sequence. It is commercially and otherwiseadvantageous to be able to produce a TM polypeptide composition having aunique N-terminal processing site, so as to avoid any potentialambiguity regarding the nature of the final product. Therefore, thenucleotide sequence encoding the N-terminal region of the polypeptidecan be modified such that the processing enzyme(s) of the host cell willgenerate a single N-terminus of the mature polypeptide. This can beaccomplished, e.g., by deleting the N-terminal three amino acids whichconstitute one of the processing sites, which results in a fullyfunctional polypeptide that starts at amino acid 4 (Glu) of the nativeTM. This further provides a polypeptide having only a single and uniquepost-processing N-terminus. Other functional constructs can also beprepared routinely, having other single N-termini, either throughfurther deletion of the native TM N-terminus or through substitution ofalternative homogeneous N-terminal processing sites.

L. Production of Thrombomodulin Analogs Having a Unique C-terminus

A still further modification which can be made in accordance with thegoals of this invention is to modify the TM analog composition so itexhibits a unique carboxy terminus. Providing single-chain materialensures elimination of at least one C-terminus in accordance with theprocedures disclosed herein. One particularly advantageous constructprovides a TM analog which is resistant to proteases or other factors,e.g., post-translational processing enzymes or C-terminal exoproteases,by providing a C-terminus which is resistant to degradation. Theseanalogs are provided by modifying the DNA coding for the C-terminalamino acids of the polypeptide. For example, as disclosed herein, theC-terminus of the functional analog ending at amino acid 497 of nativeTM can conveniently be shortened by 7 amino acids to provide aC-terminus ending in a -Pro-Pro sequence which is particularlyprotease-resistant. Other amino acid deletions and substitutions whichprovide biologically active TM analogs can be prepared in accordancewith routine modifications of the methods known in the art and asdescribed herein.

M. Formulation and Use of Thrombomodulin Analogs

The soluble TM analogs described herein may be prepared in a lyophilizedor liquid formulation. The material is to be provided in a concentrationsuitable for pharmaceutical use as either an injectable or intravenouspreparation.

These compounds can be administered alone or as mixtures with otherphysiologically acceptable active materials, such as antibiotics, otheranticoagulants, one-chain t-PA, or inactive materials, or with suitablecarriers such as, for example, water or normal saline. The analogs canbe administered parenterally, for example, by injection. Injection canbe subcutaneous, intravenous or intramuscular. These compounds areadministered in pharmaceutically effective amounts and often aspharmaceutically acceptable salts, such as acid addition salts. Suchsalts can include, e.g., hydrochloride, hydrobromide, phosphate,sulphate, acetate, benzoate, malate, citrate, glycine, glutamate, andaspartate, among others. See, e.g., Remington's Pharmaceutical Sciences(17th ed.), Mack Publishing Company, Easton, Pennsylvania, and Goodman &Gilman's, The Pharmacological Bases of Therapeutics, 8th ed., PergamonPress, 1985, both of which are herein incorporated by reference. Theanalogs described herein may display enhanced in vivo activity byincorporation into micelles and/or phospholipid aggregates. Methods forincorporation into ionic detergent aggregates or phospholipid micellesare known.

An antithrombotic agent can be prepared using the soluble TM analogsdescribed herein and can consist of a completely purified analog aloneor in combination with a thrombolytic agent as described above.Compounds of the present invention which are shown to have the aboverecited physiological effects can find use in numerous therapeuticapplications such as, for example, the inhibition of blood clotformation. Thus, these compounds can find use as therapeutic agents inthe treatment of various circulatory disorders, such as, for example,coronary or pulmonary embolism, strokes, as well as the prevention ofreocclusion following thrombolytic therapy, and these compounds haveutility in the cessation of further enlargement of a clot during aninfarction incident. Further, the compounds disclosed can be useful fortreatment of systemic coagulation disorders such as disseminatedintravascular coagulation (DIC), which is often associated withsepticemia, certain cancers, and toxemia of pregnancy.

These compounds can be administered to mammals for veterinary use, suchas with domestic animals, and for clinical use in humans in a mannersimilar to other therapeutic agents, that is, in a physiologicallyacceptable carrier. In general, the administration dosage for the TManalog will range from about at least 0.0002, more usually 0.02, andless than 5000, usually less than 2000, more usually less than 500μg/kg, usually 0.02 to 2000 μg/kg and more usually 0.02 to 500 μg/kg ofthe host body weight. These dosages can be administered by constantinfusion over an extended period of time, until a desired circulatinglevel has been attained, or preferably as a bolus injection. Optimaldosages for a particular patient can routinely be determined by one ofordinary skill in the art.

Without further elaboration, it is believed that one skilled in the artcan, using the preceding description, utilize the present invention toits fullest extent. The following preferred specific embodiments are,therefore, to be construed as merely illustrative and not limitative ofthe remainder of the disclosure in any way whatsoever.

In the foregoing and in the following examples, all temperatures are setforth uncorrected in degrees Celsius; and, unless otherwise indicated,all parts and percentages are by weight.

The entire disclosures of all applications, patents, and publications,cited above and below, are hereby incorporated by reference.

EXAMPLES

The first four examples which follow are directed primarily towardTM_(E) (Sf9). Similar methods are applicable with routine modificationsto the TM_(LEO) made in mammalian cells, as described in the laterexamples.

EXAMPLE 1 Isolation and Expression of TM Analog Sequences

A. Cloning

Genes for producing recombinant thrombomodulin analog peptides wereisolated as described in copending applications U.S. Ser. No. 345,372,filed 28 Apr. 1989, U.S. Ser. No. 406,941, filed 13 Sep. 1989, and PCTSerial No. 90/00955, filed 16 Feb. 1990, each herein incorporated byreference. Briefly, human DNA was used to isolate a gene encoding the 6EGF-like domains of thrombomodulin corresponding to amino acids 227-462as well as other portions of the thrombomodulin peptide. (See Table 1).This DNA was isolated from fetal liver according to the method of Blin,N and DW Stafford, (1976) Nucleic Acids Res. 3:2302. The DNA was thenused as a template in a polymerase chain reaction with syntheticallyderived primers selected to embrace the desired regions (See-Tables 3 &4). See e.g., Innis et al., PCR Protocol, A Guide to Methods andApplications (1990), Academic Press.

1. Isolation of genes encoding amino acids 227-462

The following steps provide a means to obtain a DNA insert encodingamino acids (aa) 227-462 and uses primers #1033 and #1034 (See Table 3).It is understood that by modifying the procedures set forth below byusing alternative primers, other soluble TM analogs can be obtained.

The sequence of the #1033 and #1034 primers correspond to the 5' and 3'ends of the desired domain, but they have been modified so that theycontain a BamHI site. A termination codon (TGA) was introduced followingbase 1586. The polymerase chain reaction was run under the conditionsdescribed by Saiki, et al., (1988) Science 320:1350-1354, except thatthe initial temperature of annealing was 37° C. After 10 cycles, theannealing temperature was raised to 45° C. for the remaining 30 cycles.An aliquot of the reaction products was separated on a 5% polyacrylamidegel and visualized by ethidium bromide staining. A band of the predictedsize (700 bp) could clearly be seen. Alternatively one can sequence thisband or hybridize it to an internal probe to confirm its identity.

2. Isolation of genes encoding other regions of thrombomodulin

The polymerase chain reaction as herein described was used in the samemanner to isolate additional fragments of thrombomodulin correspondingto the regions listed in Table 4. In particular, these regions embraceone or more of the EGF-like domains and the O-linked glycosylationdomain. The sequences of the primers selected to produce the desiredregions are shown in Table 3.

3. Cloning plasmids containing the thrombomodulin analog genes

The remainder of the polymerase chain reaction mixture described above(i) was restricted with BamHI, separated on a 5% polyacrylamide gel, andthe 700 bp band was excised and eluted. It was ligated to pUC19 that hadbeen restricted with BamHI and the new plasmid was transformed into E.coli strain DH5-alpha. Recombinant colonies were selected on a mediumcontaining ampicillin and 5-bromo-4-chloro-3-indolyl-β-D-galactoside.White colonies were picked onto a grid and hybridized by theGrunstein-Hogness technique with a synthetically derived genecorresponding to aa 283-352 of thrombomodulin that had been cut out of acloning plasmid (pTM2.1) with EcoRI and HindIII before labelling with ³²P by random priming (Boehringer Mannheim).

After exposing the filters to X-ray film the one colony that hybridizedto the pTM2.1 probe was selected -and a culture grown up. DNA wasextracted and analyzed by restriction with either BamHI or BglII toconfirm the presence of an insert with the correct restriction map. Theexcised insert was also transferred to nitrocellulose and analyzed byhybridization with labelled pTM2.1. Both methods confirmed that the 700bp insert contained the coding sequence for the 6 EGF-like domains ofthrombomodulin. The insert was sequenced to verify that no mutations hadbeen inadvertently introduced during the PCR procedure. The plasmidcontaining the desired gene fragment is named pUC19pcrTM7.

B. Expression of TM

1. Construction of AcNPV Transfer Vectors

The transfer vectors described below are also described in copendingapplication U.S. Ser. No. 07/812,892, which is a continuation of U.S.Ser. No. 07/345,372. The transfer vectors contain the Hypodermin Asignal sequence from Hypoderma lineatum.

i. pHY1 and pSC716

Oligomers containing the Hypodermin A signal sequence, a translationinitiation codon, a BglII cloning site, a BamHI 5' overhang and a Kpnl3' overhang, COD#1198 and COD#1199 (see Table 2), were annealed andcloned into pSC654, a pUC19 derivative, creating pHY1. Plasmid pHY1 wasrestricted with BamHI and EcoRI, releasing the hypodermin A signalsequence. This sequence was then ligated to pSC714 to create the vectorpSC716. Plasmid pSC714 is a derivative of pVL1393, obtained fromSummers, et al. The only difference between the two is that in pSC714,one of the BglII sites has been destroyed.

ii. Construction of pHY101

The BamHI fragment from pUC19pcrTM7 (see Aiii above) was cloned into theBglII site of pHY1 and the orientation was chosen such that thehypodermin A signal sequence was adjacent to amino acid 227. Thisplasmid is pHY101.

iii. Construction of the AcNPV transfer vector pTMHY101

Plasmid pHY101 was treated with BamHI/EcoRI which releases theHypodermin A signal sequence linked to the TM analog coding sequence.Shuttle vector pVL1393 contains a partially deleted AcNPV polyhedringene and unique BamHI and EcoRI cloning sites. The BamHI/EcoRI fragmentfrom pHY101 was inserted downstream of the polyhedrin promoter, thuscreating a plasmid, pTMHY101, in which the hybrid gene was under thecontrol of the polyhedrin promoter.

iv. Construction of other ACNPV transfer vectors

Transfer plasmids containing other TM analog gene sequences wereconstructed using a strategy similar to that outlined above. Fragmentsfrom the cloning plasmids described above were cloned into pSC716 inframe so that the TM analog gene sequence was fused to the hypodermin Asignal sequence. The TM gene sequences are listed in Table 4.

v. Production of pure phage stocks

Cell transfection was done using a calcium phosphate precipitationtechnique modified for insect cells according to Summers and Smith.Briefly, a T25 flask was seeded with 2×10⁶ Sf9 cells, and the cells wereallowed to attach for one hour at room temperature. Two μs of transfervector, for example, pTHR28, and 1 μg of AcNPV DNA were coprecipitatedin calcium phosphate and incubated with the cells for 4 hours. The cellswere rinsed and re-fed with growth media, then placed in a 28° C.incubator for 3-4 days. During this incubation, the cells produce bothrecombinant and non-recombinant virus which accumulate in the growthmedia. This media, containing a mixed viral stock, was assayed for thepresence of protein C cofactor activity (see below).

Recombinant viruses were detected by plaque assay. The transfectionstocks were diluted (10⁻⁴, 10⁻⁵, and 10⁻⁶) and plated 4-7 dayspost-transfection. Occlusion negative (recombinant) plaques were picked7 days after plating and replated (10⁻¹, 10⁻², and 10⁻³ dilution). Afteranother 7 days, the plates showed 100% pure occlusion-negativerecombinant plaques. A single pfu from each was selected for production.A high titer viral stock was grown by infecting 5 mls of Sf9 cells (×10⁶/ml in Excell 400 medium (JR Scientific)) with a single pfu, grown for4-5 days. A portion of this stock was then diluted 1:50-1:100 into Sf9cells grown to mid-log phase to produce a protein stock.

2. Production of Human TM Analogs in Mammalian Cells

i. Mammalian expression vectors for TM analogs

This example provides a mammalian expression vector comprising theanalog genes of Example 1, A. Genes can be operably linked to the signalsequence of human tissue plasminogen activator (see Table 2). Theexpression plasmid, pPA124, contains a promoter contained within thethree copies of the long terminal repeats derived from Harvey Sarcomavirus for the expression of cloned genes. This plasmid was derived frompPA119, and pSC672, both described in detail in co-pending U.S. Ser. No.251,159, filed Sep. 29, 1988, incorporated herein by reference. ABglII-BclI fragment containing the SV40 polyadenylation region wasisolated from pSC672. This fragment was cloned into pPA119 which hadbeen digested with BglII and BclI. In the resulting plasmid, pPA124,both the BglII and BclI sites remained intact. Plasmid pPA124 containsthe t-PA signal sequence adjacent to an appropriate restriction site andthis signal sequence also contains the second intron of the human t-PAgene.

The gene encoding the soluble TM analog was removed from pUC19pcrTM7 bytreatment with BamHI and ligated to pPA124 that had been treated withBglII. Transformants were screened for the presence of the insert in thecorrect orientation, that is, in which the t-PA signal sequence waslinked to the 5' end of the thrombomodulin insert encoding an openreading frame. This plasmid, pTM101, was then digested with ClaI andligated to a ClaI fragment containing the dhfr gene under the control ofthe SV40 promoter. The ClaI fragment is described in WO88/02411 at page26. Transformants were screened for the presence of this dhfr cassetteand then the orientation relative to the plasmid was determined byrestriction mapping (pTM103).

Plasmid pTM103, containing the dhfr sequence in the divergent directionto the thrombomodulin sequence, was treated with BclI. A DNA fragmentencoding a gene providing hygromycin resistance on a BamHI fragment wasligated into the plasmid. Clones were selected, after transformationinto E. coli strain DH5α, by their ability to grow on plates containingboth ampicillin and hygromycin B. The orientation of the hygromycin Bgene relative to the plasmid was determined by restriction mapping. Oneplasmid, pTM108, in which the hygromycin B gene lies in the oppositeorientation to the TM gene, was grown up in culture. This plasmid hasthe sequences encoding the TM analog under the control of the triple LTRpromoter, with both a gene that confers hygromycin B resistance and onethat encodes dhfr present on the plasmid. A similar expression plasmid,pTHR13, also contains the t-PA signal sequence operably linked to thesequence encoding the 6 EGF-like domains both under the control of thecytomegalovirus promoter. This plasmid contains the M13 origin ofreplication making it useful for site directed in vitro mutagenesis,described below. The thrombomodulin sequence was linked to the tissueplasminogen activator signal sequence, ensuring its secretion. The TManalog produced by both these plasmids, 4t/227-462, is comprised of the6 EGF-like domains of thrombomodulin with an additional 4 amino acids onthe N-terminal end that are the result of processing of the t-PA signalpeptide.

ii. Transfection, selection and amplification of stable mammalian clones

For the transfection, 10 μg of pTM108 was mixed with Lipofectin reagent(Bethesda Research Laboratories) and added to a monolayer of 10⁵ CHL-1host cells in 6-well plates. Forty-eight hours after transfection, aknown number of cells were plated onto selective media. Resistance tohygromycin B was used as the selection marker. CHL-1 cells transfectedwith the bacterial hygromycin B gene can survive growth in 0.3 mg/mlhygromycin B.

The transfection or selection frequency was 2 in 10³ and was determinedas the number of colonies arising after selection, divided by the totalnumber of cells plated. The culture supernatant was shown to contain 1.5U/ml TM activity after 24 hours in contact with the cells.

A population of cells resistant to the first selection conditions werethen subjected to a second round of selective pressure. Either 100 nM or500 nM methotrexate (MTX) was added to the growth medium to select fortransfectants that expressed the dhfr gene. Only clones which hadamplified the dhfr gene would be able to grow in this high level of MTX.In the process of gene amplification, other plasmid sequences will beco-amplified with the dhfr gene and thus lead to increased geneexpression of the non-selectable gene as well. Resistant clones wereapparent after 5 to 6 weeks. Individual clones resistant to these levelsof MTX were isolated and assayed. A culture after selection in 100 nMMTX was shown to produce 4.9-14.7 U per ml of protein C activatingactivity (see below). A pooled population was plated into a ten-foldgreater concentration of MTX (1 μM or 5 μM). Clones were again recoveredfrom this selection step and assayed. At each step clones were shown toproduce and secrete TM analog into the culture medium.

C. Site-Directed Mutagenesis

The 6 EGF-like domains region of native thrombomodulin has twomethionine residues, one at position 291 and one at position 388. (SeeTable 1). Site-directed in vitro mutagenesis was used to convert eitheror both of these methionines to other amino acids. Site-directedmutagenesis uses a synthetic DNA sequence containing a desirednucleotide substitution, insertion, or deletion to specifically alterthe nucleotide sequence of a single-stranded template DNA. Hybridizationof this synthetic DNA to the template and subsequent primer extensionproduces a heteroduplex DNA capable of cell transformation to yield thedesired mutation. A diagram depicting this process is shown in FIG. 1 ofU.S. patent application Ser. No. 07/568,456.

A similar method can be used to eliminate potential protease-sensitiveregions, to modify glycosylation sites, and to modify the amino acidcarboxy termini of the desired TM analog.

A plasmid for making single stranded DNA copies, pTHR14, was constructedby ligating the F1 origin of replication contained on an AseI-ScaIfragment into an insect cell transfer vector, pTMHY101, previouslydigested with NdeI and ScaI. Plasmid pTMHY101 contains a gene sequencethat produces a peptide corresponding to the 6 EGF-like domains ofthrombomodulin, amino acids 227-462, and is described above. pTMHY101 isdescribed in copending application U.S. Ser. No. 345,372 as well asB(1)(iii) above. A similar vector containing the lectin domains, 6 EGF,and O-linked domains was used for mutagenizing and constructing thepTHR525, which encodes one preferred embodiment.

Specific mutagenizing oligonucleotide primers were synthesized and usedwith the MUTATOR™--DNA Polymerase III Site-directed Mutagenesis Kit(Catalogue #200500, Stratagene, La Jolla, Calif.), except as otherwisenoted, to prime second strand synthesis and create thrombomodulin analoggenes with either one or both of the methionines changed to anon-oxidizable amino acid. Primers directing conversion to the preferredamino acids leucine, glutamine, or alanine are shown in Table 5. Alsoincluded in these primers are substitutions in the nucleotide sequencethat add a unique restriction enzyme site useful as a diagnostic forsuccessful mutagenesis but which do not necessarily change thecorresponding amino acid sequence. The nucleotide substitutions areunderlined in the primers shown in Table 5. For example, in plasmidpTHR28 the methionine at position 388 in the native thrombomodulinprotein was replaced with leucine, and in the process a unique PvuIIsite was introduced. It is understood that other substitutenon-oxidizable amino acids would be equally useful in this embodiment ofthe present invention.

Purified single-stranded DNA templates were prepared using the proceduredescribed by Bio-Rad (Muta-Gene Phagemid in vitro Mutagenesis,Instruction Manual, Cat. no. 170-3576, pages 33-34) although otherprocedures known in the art would be equally suitable.

The 5' terminus of each mutagenizing primer was phosphorylated byincubating 0.5 ng/μl of primer in a solution containing 2 mM rATP, 0.4U/μl polynucleotide kinase in annealing buffer (20 mM Tris-HCl pH 7.5, 8mM MgCl₂, and 40 mM NaCl) at 37° C. for 30 minutes. The reaction washeat inactivated by incubating the mixture at 65° C. for 15 minutes.Phosphorylation increases the rate of successful mutation. Thephosphorylated primer was annealed to the single-stranded template byheating 100 ng of template and 2.5 ng of primer in 25 μl of annealingbuffer to 65° C. for 5 minutes then allowing the mixture to cool andanneal at room temperature for 10 minutes. Double stranded DNA was madeby primer extension essentially as described by Tsurushit, N., et al.,(1988) Gene 62:135-139, and O'Donnell, M. E., et al., (1985) J. Biol.Chem. 260:12875-12883. Briefly, the template/primer mixture was diluted(1:1) with 10% annealing buffer plus 80 μg/ml bovine serum albumin, 2.5mM dithiothreitol, 0.25 mM mixed dNTPs, 2 mM rATP and 1% glycerol plus 1μg of single-stranded DNA binding protein. The reaction was incubatedfor 5 minutes at room temperature to allow the binding protein to coatthe single-strand DNA template. DNA polymerase III holoenzyme (E. coli,1.7 μl of 50 U solution) was added, and the reaction was incubated at30° C. for 10 minutes. T4 DNA ligase was added (0.5 μl, 2 Weiss units)and the reaction was further incubated for 5 minutes at 30° C. Thismixture was used to transform E. coli and properly mutated clones wereselected by restriction digest pattern.

This same process can be used to make mutants that can be expressed inmammalian cells using, for example, pTR13 (described above) which has anM13 origin of replication for making single stranded DNA templates.

D. Production and Purification of Recombinant Protein

T25 flasks were seeded at a density of 2-10⁶ Sf9 cells in 5 ml TMN-FHmedia plus 10% FBS or Excell 400, then infected with an isolatedrecombinant plaque from Part B or C above. Viral stocks were collectedafter three days. Flasks (30-100 ml shaker flasks or 100-300 ml spinnerflasks) were seeded with cells (1-1.8×10⁶ /ml) and infected withaliquots of the viral stock equal to 1/50 th to 1/100 th of the finalvolume. The infected cell cultures were grown for four days beforeharvesting the conditioned media containing recombinant oxidationresistant TM analog protein.

The TM analogs were purified from conditioned media by removal of celldebris, followed by five chromatography steps: 1) Q Sepharose, 2)thrombin affinity, 3) gel filtration, 4) anion exchange, and 5) a secondgel filtration step. The gel filtration steps effect an exchange ofbuffers. All chromatography steps were performed at 4° C.

1. Materials

Some of the chromatographic resins were purchased from commercialsources. Q Sepharose and Sephadex G25 were purchased from Sigma (St.Louis, Mo.), and Mono Q 5/5® from Pharmacia LKB (Piscataway, N.J.).

DFP-thrombin agarose was prepared approximately as follows: 360 mg ofbovine thrombin in 100 ml of 20 mM Na phosphate, pH 7.5 was added toapproximately 100 ml of a 50% Affigel 10 resin slurry and mixedovernight at 4° C. The Affigel 10 was prepared for use as described bythe manufacturer and equilibrated with the load buffer. Residual activeesters were blocked by the addition of 100 ml of 0.1M glycinemethylester (pH 5.6) for one hour at 4° C. The gel was then equilibratedwith 30 mM Tris-HCl, 2M NaCl, pH 7.5, and 20 μl of DFP was added to givea final concentration of about 1 mM DFP. After 16 hrs of mixing at 4° C.an additional 6 μl of DFP was added and mixing continued for 4additional hours. The resin was then washed with 20 mM Tris-HCl, 2M NaClpH 7.5 and stored at 4° C.

Thrombin activity was measured using the Kabi S-2238 substrate andindicated that >86% of the thrombin was removed from the solution, andpresumably coupled to the resin, giving a final concentration of about 6mg of thrombin per ml of resin. The enzymatic activity of the DFPtreated resin was <1% of the starting activity.

2. Production of Pure TM_(E) Analog Peptide

Conditioned media was harvested and clarified by centrifugation at1400×g for 10 minutes. The pH was adjusted from about 6.0 to about 5.2with glacial acetic acid. The adjusted media was then loaded onto acolumn of Q Sepharose resin. The column had previously been equilibratedwith about four column volumes of wash buffer 1 (117 mM Na acetate,0.02% NaN₃ pH 5.0). After loading, the column was washed with washbuffer 1 followed by wash buffer 2 (25 mM Na acetate, 0.1M NaCl pH 5.0)then the oxidation resistant TM analog was eluted with wash buffer 2containing 0.3M NaCl, pH 5.0.

Column fractions containing activity as measured in the protein Cactivation assay (see above) were pooled, then diluted with of 0.3MNaCl, 20 mM Tris-HCl, 0.5 mM CaCl₂, 0.02% NaN₃, pH 7.5. The pH of thediluent was measured and adjusted to about 7.5 with NaOH. The ionicstrength of the pool was about the ionic strength of a solution of 0.3MNaCl. This adjusted pool was loaded overnight by gravity onto a thrombinagarose column pre-equilibrated with the same buffer used to dilute theconditioned media. The column was washed with diluent buffer, and the TManalog was removed from the matrix with 2.0M NaCl, 20 mM Tris HCl, 1 mMNaEDTA, 0.02% NaN₃, pH 7.5.

The substantially pure TM analog was applied to a Sephadex G25 columnand recovered in 0.2% N-ethylmorpholine acetate (NEM) pH 7.0. This stepremoves NaCl.

TM analog collected from the Sephadex G25 column was applied to a Mono Qcolumn (Pharmacia, 10 micron particles, quaternary amine)pre-equilibrated with 0.2% N-ethylmorpholine (NEM) pH7.0. After washingwith this buffer the various forms were separated using a gradient of 0to 0.4M NaCl. Samples of each fraction were evaluated on an SDS-PAGE gelunder non-reducing conditions. SDS Polyacrylamide Gel Electrophoresiswas performed by the method of Laemmli using 3.3% acrylamide in thestacking and 12.5% acrylamide in the running gel. Nonreduced sampleswere diluted in Laemmli sample solubilization buffer (50 mM Tris-HCl, pH6.8, 25% glycerol, 2% SDS, and 0.01% bromophenol blue) and loadeddirectly onto the gel. Pharmacia LMW Calibration Kit protein standardswere used for MW markers, and the gels were silver stained. In somefractions, only one major band is visible with silver staining.

Fractions containing peptides with like mobilities were pooled and thenassayed for total protein content and for activity in the protein Cactivation assay as described below.

E. Assays for Thrombomodulin Analogs

1. Materials

Rabbit thrombomodulin, hirudin and human Protein C were obtained fromIntegrated Genetics or American Diagnostica. Human thrombin is availablefrom a variety of noncommercial and commercial sources. Bovine thrombinfor affinity chromatography was purchased from Miles Labs, Dallas, Tex.D-valyl-L-leucyl-L-arginine-p-nitroanilide (S-2266) andD-Phe-Pip-Arg-p-nitroanilide (S-2238) were purchased from Kabi Vitrum.

Bovine serum albumin (fraction V), citrated human plasma, and APTTreagent were purchased from Sigma Chemicals. Microtiter plates weresupplied by Dynatech (#25861-96). All other reagents were of the highestgrade available.

2. Methods and Results

i. Protein C Activation Assay (Chromogenic)

This assay was performed by mixing 20 μl each of the following proteinsin a microtiter plate: thrombomodulin sample (unknown or standard),thrombin (3 nM), and Protein C (1.5 μM). The assay diluent for eachprotein was 20 mM Tris-HCl, 0.1M NaCl, 2.5 mM CaCl₂, 5 mg/ml BSA, pH7.4. The wells were incubated for up to 2 hours at 37° C., after whichProtein C activation was terminated by the addition of 20 μl of hirudin(0.16 unit/μl, 570 nM) in assay diluent and incubation for an additional10 minutes.

The amount of activated Protein C formed was detected by adding 100 μlof 1.0 mM S-2266 (in assay diluent), and continuing to incubate theplate at 37° C. The absorbance at 405 nm in each well was read every 10seconds for 15 minutes, using a Molecular Devices plate reader. Theabsorbance data was stored, and the change in absorbance per minute(slope) in each well was calculated. The change in absorbance per minuteis proportional to pmole/ml of activated Protein C.

This ratio was determined empirically using varying concentrations oftotally activated Protein C. Samples containing fully activated ProteinC were generated by mixing Protein C at 0 to 1.5 μM with 60 nM rabbit TMand 30 nM thrombin, incubating for 0 to 4 hours, adding hirudin andmeasuring S2266 activity as above. Conditions under which the Protein Cwas fully activated were defined as those in which the S2266 activity(A405/min) reached a plateau.

A unit of activity is defined as 1 pmole of activated Protein Cgenerated per ml/min under the reagent conditions defined above.Alternatively, activity values are reported in comparison to nativedetergent solubilized rabbit thrombomodulin or another thrombomodulinstandard.

ii. Protein C Cofactor Activity After Exposure to Oxidants

Chloramine-T (N-Chloro-p-toluenesulfonamide sodium salt, Sigma) was usedto specifically test the resistance of the mutant TM analog peptides tooxidation. Transfection culture supernatant (1 ml) containing a peptideencoded by a mutant TM gene sequence or pTMHY101 (wild-type, aa 227-462)was desalted into 1.5 ml of 0.2% N-ethylmorpholine (NEM), pH 7.0, 0.008%Tween 80 on a NAP-10 column (LKB/Pharmacia) and then lyophilized andresuspended in 100 μl of the above buffer. The sample was dividedequally and either 5 μl of water (control) of 5 ul of 0.1M chloramine-T(final conc.=9.1 mM) was added. The samples were incubated at roomtemperature for 20 minutes, then passed over the NAP-5 column to removeany oxidant. The desalting buffer used was protein C assay diluent. Themutant peptide retained all of its activity after being exposed tochloramine-T whereas the wild type peptide was substantiallyinactivated.

iii. Inhibition of the Activated Partial Thromboplastin Time (APTT)

The formation of a clot from citrated plasma is triggered by theaddition of brain cephalin in ellagic acid ("APTT reagent"), and calciumion. The time required for the clot to form is reproducible andincreases proportionally with the addition of thrombomodulin. Reagentsfor the APTT are incubated at 37° C. before mixing, except for thecitrated plasma, which is kept at 4° C.

The reaction was carried out as follows: 100 μl of Sigma Citrated Plasmawas added to a plastic cuvette (Sarstedt #67.742), incubated at 37° C.for 1 min; 100 μl of Sigma APTT reagent was added and the mixtureincubated for 2 min at 37° C.; 100 μl of test sample (or control buffer)and 100 μl of 25 mM CaCl₂ were added and the cuvette was immediatelyplaced in a Hewlett-Packard 8451A spectrophotometer equipped with aHaake KT2 circulating water bath to keep the cuvette at 37° C. duringreading. The absorbance due to light scattering at 320 nm was measuredevery 0.5 seconds, from 15 to 120 seconds, timed from the addition ofCaCl₂. A plot of absorbance vs. time yields a sigmoidal curve, with theclotting time defined as the time at which the slope is the steepest,corresponding to the inflection point of the curve.

Ex vivo APTT assays were performed in the manner described above withthe exception that citrated plasma from the animal used in the in vivoexperiment was used in place of the citrated plasma obtainedcommercially.

Alternatively, an APC or TCT assay can be performed as described.

iv. Inhibition of thrombin clotting time (TCT) and prothrombin reaction(PT)

Both the PT and TCT are determined using the Hewlett-Packard 8452Adiode-array spectrophotometer or an equivalent used for the APTT. Forthe PT reaction, 90 μl of either TM analog 6h/227-462 or PBS was addedto 20 μl thromboplastin and 90 μl 25 mM CaCl₂ in a cuvette. The mixturewas incubated for 1 minute at 37° C., then 100 μl of citrated plasma wasadded. After loading the cuvette into the spectrophotometer, theabsorbance due to light scattering at 320 nm was measured every 0.5seconds, from 15 to 120 seconds, timed from the addition of the plasma.A plot of absorbance vs. time yields a sigmoidal curve, with theclotting time defined as the time at which the slope is the steepest,corresponding to the inflection point of the curve. The TCT is evaluatedin the same manner. The initial reaction mixture contains 100 μlcitrated plasma, 25 μl of 100 mM CaCl₂, and 162.5 μl of either PBS or TManalog. After 1 minute, 12.5 μl of thrombin is added. The clotting timeis measured as described above.

V. Direct anticoagulant activity--Inhibition of thrombin catalyzedconversion of fibrinogen to fibrin

Thrombin and varying amounts of TM analog 6h/227-462 were incubated for2 minutes at 37° C. in microtiter plate wells. The total initialreaction volume was 50 μl PBS plus 7.5 mM CaCl₂, and 90 nM thrombin.After initial incubation, 100 μl of 3.75 mg/ml human fibrinogen wasadded per well, and the thrombin induced formation of fibrin wasfollowed by measuring the change in absorbance at 405 nm in a MolecularDevices Vmax spectrophotometer (Molecular Devices, Menlo Park, Calif.).The end-point of the assay was the time at which 50% of the finalabsorbance was reached. Residual thrombin activity was determined byreference to a thrombin standard curve, which linearly relates thereciprocal of the thrombin concentration to the clotting time. Whenamounts of detergent solubilized native rabbit thrombomodulin and TManalog 6h/227-462 exhibiting equal activity as measured by protein Ccofactor activity are compared in the direct anticoagulant activityassay, the TM analog exhibits a significantly reduced ability to inhibitthrombin-mediated conversion of fibrinogen to fibrin (approximately1/10).

vi. Inhibition of platelet activation and aggregation

The effects of TM analog 6h/227-462 on thrombin activation of plateletswas tested by the methods of Esmon, et al., (1983) J. Biol. Chem.258:12238-12242. When evaluated using this assay, TM analog 6h/227-462did not significantly inhibit the thrombin-mediated activation andaggregation of platelets.

viii. Additional measures of TM antithrombotic activity

1) TM analog's inhibition of activation of Factor V by thrombin ismeasured by the method described by Esmon et al., J. Biol. Chem.,(1982), 257:7944-7947.

2) Inhibition of the TM analog thrombin complex by antithrombin III andheparin cofactor II is measured as described by Jakubowski et al.(1986), supra.

3) TM analog's inhibition of the inactivation of protein S by thrombinis measured by the method described by Thompson & Salem, J. Clin.Invest., (1986), 78(1):13-17.

4) Inhibition of thrombin-mediated activation of Factor XIII is measuredby, the method of Polgar, et al., (1987) Thromb. Haemostas. 58:140.

EXAMPLE 2 In vivo Activity of a TM Analog in a Rodent Model of DeepVenous Thrombosis

The ability of a TM analog to abrogate the formation of a thrombus wasevaluated in a modified stasis/endothelial injury-induced venousthrombosis model in the rat (see Maggi, A. et al., (1987) Haemostasis17:329-335 or Pescador, R. et al., (1989) Thrombosis Research53:197-201). The vena cava of an anaesthetized male Sprague Dawley rat(450 gr) was surgically isolated, then the animal was treated by bolusinjection into the femoral artery with a thrombomodulin analog(6h/227-462 which contains the 6 EGF-like domains of nativethrombomodulin), standard heparin or normal saline (0.1 ml/rat), as acontrol. The dose of heparin was 45 units/rat. The dose ofthrombomodulin analog was 100, 10, 1, 0.1 or 0.01 μg/rat. Two minutespost-injection, the inferior vena cava was ligated at the left renalvein to induce stasis, and the vascular endothelium was injured bygently pinching with forceps. After 10 minutes, the vena cava wasexcised and examined for the presence of a thrombus, which if presentwas removed and weighed. In all cases the animals treated with heparinor thrombomodulin analog (6h/227-462) at 100, 10, or 1 μg/rat showed noevidence of thrombus formation whereas the saline treated animals andthose receiving the lowest dose of thrombomodulin analog (0.01 μg) hadthrombi with an average weight of 14.9 mg/thrombus. The rats treatedwith 0.1 μg of thrombomodulin analog showed a trace amount of thrombuswhich was not large enough to be removed and weighed.

The dose range used in this study was selected based on an in vitro APTTassay in which 1 μg/ml of thrombomodulin analog was insufficient toprolong the APTT but the addition of 10 μg/ml resulted in a significantprolongation. The results of APTT assays done on plasma samples takenfrom each of the treated rats show no prolongation in the TM analogtreated and control rats (100 μg TM analog=45 sec, all other doses TManalog and the saline controls=30-35 sec). However, the APTT in theheparin treated rats was significantly prolonged (100 sec.).

This experimental system is a directly comparable model for deep venousthrombosis in humans, which is characterized by vascular injury andreduced blood flow. The results described above demonstrate that verylow doses of a TM analog that are able to act as a cofactor forthrombin-mediated activation of protein C yet have a substantiallyreduced ability to inhibit thrombin-mediated conversion of fibrinogen tofibrin are effective at preventing thrombus formation. Moreover, theabsence of prolongation in the APTT measured ex vivo indicates that thisTM analog has no systemic effect on coagulation parameters and,therefore, would not promote unsafe bleeding side effects.

EXAMPLE 3 In vivo Activity of a TM Analog in a Primate Model of BothVenous and Arterial Thrombosis

The antithrombotic properties of the thrombomodulin analogs wereevaluated in an arteriovenous shunt model in the baboon using a slightmodification of the method of Cadroy, Y. et al., (1989) Journal ofLaboratory and Clinical Medicine 113:436-448, as described in Hanson S.R. and Harker, L. A. (1987) Thrombosis and Haemostasis 58:801-805. Thismodel was chosen because of the hemostatic similarity between the baboonand man and because the arteriovenous shunt serves as a model for botharterial-type and venous-type thrombi.

A silastic tubing shunt, modified with a piece of dacron tubing (3.2 mmin diameter) followed by a teflon chamber (9.3 mm in diameter), wasinserted into the femoral artery of the baboon such that blood flowedout of the artery through the shunt and returned to the baboon via thefemoral vein (see FIG. 2 of U.S. patent application Ser. No.07/568,456). The dacron tubing presents a thrombogenic surface whichstimulates the natural coagulation process, and in particular thedeposition of platelets on the graft surface, and serves as a model forthe generation of arterial, i.e. platelet rich, thrombi held together byfibrin. The chamber creates a stasis condition similar to that found inveins, where the rate of flow of the blood is reduced, and in particularmimics the area around venous valves, thus modeling flow conditionssimilar to those resulting in deep venous thrombosis. The thrombi formedin the chambers are venous-type, fibrin rich thrombi. Venous-typethrombi also contain platelets, but fewer than arterial-type thrombi.Thrombus formation in either the dacron graft or chamber is evaluated bymeasuring both platelet deposition and fibrin accretion. Plateletdeposition is measured by removing platelets from the baboon,radiolabeling the platelets with ¹¹¹ indium-oxine using the method ofCadroy, Y,. et al., (1989) Journal of Clinical and Laboratory Medicine113(4):436-448, and then returning them to the animal. A scintillationcamera, such as a Picker DC 4/11 Dyna scintillation camera (PickerCorp., Northford, Conn.), is positioned over the graft to directlymeasure the amount of radioactivity from the platelets being depositedas part of a thrombus as described in Cadroy, Y., et al., supra. As asecond measure of thrombus formation, a 5 μCi dose of ¹²⁵ I-labeledbaboon fibrinogen is given intravenously prior to insertion of theshunt. At the conclusion of the experiment, the shunt is removed,washed, and stored for 30 days to allow for the decay of ¹¹¹ indiumradioactivity (half-life, 2.8 days). As ¹¹¹ indium decays much morerapidly than 125iodine, the detectable radioactivity remaining in theshunt represents the amount of fibrin deposited as part of a thrombus.Total fibrin deposition is calculated by dividing the counts per minutedeposited by the amount of clottable fibrinogen present in the baboonblood as measured by the TCT assay. The first shunt in the series actsas a control for the second shunt.

Two shunts in series were inserted into a baboon and the TM analog(6h/227-462, see Table 4) infused at a point between the two shunts at arate of 7 or 8 mg/hr for one hour. As can be seen in FIG. 3 of U.S.patent application Ser. No. 07/568,456, platelets were deposited in boththe chamber and the dacron graft in the control shunt, however, plateletdeposition was significantly reduced following infusion of the TM analoginto the second shunt.

These experiments demonstrate that a TM analog that has the ability toact as a cofactor for thrombin-mediated protein C activation and has asignificantly reduce ability to inhibit thrombin-mediated conversion offibrinogen to fibrin and thrombin-mediated activation and aggregation ofplatelets can prevent the formation of either arterial-type orvenous-type thrombi in an in vivo model. Such a TM analog wouldtherefore be useful for pharmaceutical treatment of any thromboticdisease, whether localized to the arteries or to the veins.

EXAMPLE 4 In Vivo circulating Half-life

The circulating half-life of several TM analogs was evaluated using amodification of the protocol of Bakhit, C., et al., (1988) Fibrinolysis2:31-36. Thrombomodulin analog was radiolabeled with ¹²⁵ iodineaccording to the lactoperoxidase method of Spencer, S. A., et al.,(1988) J. Biol. Chem. 263:7862-7867. Approximately 100,000 cpm amount oflabeled analog was injected into the femoral vein of an anesthetizedmouse and small samples collected at selected time intervals. The levelof radioactivity present in each sample, corresponding to the amount ofradiolabeled thrombomodulin analog present in the circulation, wasdetermined by counting in a gamma counter (Beckman) and the timenecessary to decrease the amount of radioactivity in the circulation toone-half of its original value determined. These can also be based uponan APC assay and ELISA determination

Three thrombomodulin analogs were evaluated using this method:6h/227-462 (see above), 6h/227-462 that had been pretreated withhydrofluoric acid (HF) to remove some or all of the carbohydrate, and4t/227-462 (See Table 4 and Example 1.B.2). The treatment was doneaccording to the method of Mort, A. J. and Lamport, T. A. (1977)Analytical Biochemistry 82:289-309. Briefly, 0.8 mg of TM analog(6h/227-462) was incubated in 1 ml anisole+10 mls HF (conc) at 0° C. for1 hour under vacuum. After this time the volatile liquid was evaporatedand the protein residue rinsed from the reaction chamber with two, 3 mlwashes of 0.1M acetic acid followed by two 3 ml washes of 50% aceticacid. The combined washes were extracted with 2 mls of ethylether toremove any residual anisole. The peptide containing aqueous phase wasdesalted on a PD10 column with 92% of the protein recovered from thestarting material.

As can be seen from the results in Table 6, treating the TM analog so asto modify glycosylation can significantly alter its circulatinghalf-life. This can be accomplished by either removing carbohydrate oraltering its composition by expression in different cell types.

                                      TABLE 1    __________________________________________________________________________    GGCACGGCGCAGCGGCAAGAAGTGTCTGGGCTGGGACGGACAGGA46    CGGACAGGAGAGGCTGTCGCCATCGGCGTCCTGTGCCCCTCTGCTCCGGC96    ACGGCCCTGTCGCAGTGCCCGCGCTTTCCCCGGCGCCTGCACGCGGCGCG146     ##STR1##     ##STR2##     ##STR3##     ##STR4##     ##STR5##     ##STR6##     ##STR7##     ##STR8##     ##STR9##     ##STR10##     ##STR11##     ##STR12##     ##STR13##     ##STR14##     ##STR15##     ##STR16##     ##STR17##     ##STR18##     ##STR19##     ##STR20##     ##STR21##     ##STR22##     ##STR23##     ##STR24##     ##STR25##     ##STR26##     ##STR27##     ##STR28##     ##STR29##     ##STR30##     ##STR31##     ##STR32##     ##STR33##     ##STR34##     ##STR35##     ##STR36##     ##STR37##     ##STR38##     ##STR39##     ##STR40##     ##STR41##     ##STR42##    __________________________________________________________________________     ##STR43##

                  TABLE 4    ______________________________________    Vector     TM a.a. Region Domain    ______________________________________    Expression in Insect Cells    pTMHY101   aa 221-462     EGFs 1-6    pTMHY102   aa 216-468     EGFs 1-6    pTMHY103   aa 216-464     EGFs 1-6    pTHR10     aa 227-462     EGFs 1-6    PTHR11     aa 227-462:227-462                              EGFs 1-6 + EGFs 1-6    pTHR22     aa 350-462     EGFS 4, 5 & 6    pTHR78     aa 227-497     EGFs 1-6 + O-linked                              glycosylation domain    pTHR13     aa 227-462     EGFs 1-6    Expression in Mammalian Cells    pTHR13     aa 227-462     EGFs 1-6    pTHR19     aa 350-462     EGFs 4,5&6    pTHR20     aa 227-462:227-462                              EGFs 1-6 + EGFs 1-6    pTHR21     aa 227-497     EGFs 1-6 + O-linked                              glycosylation domain    ______________________________________

                  TABLE 5    ______________________________________    Primers for replacing the Methionine at aa 291    Native Sequence    Pro Asp Gln Pro Gly Ser Tyr Ser Cys Met    CCCC GAC CAG CCG GGC TCC TAC TCG TGC ATG    CCCC GAC CAG CCG GGC TCC TAC AGC TGC CTG    Mutant Primer 1580         Leu    CAG CCG GGC TCC TAC TCG TGC CAG    Mutant Primer 1581         Gln    CCCC GAC CAG CCG GGC TCC TAC TCG TGC GCA    Mutant Primer 1582         Ala    Cys Glu Thr Gly Tyr Arg Leu Ala Ala    TGC GAG ACC GGC TAC CGG CTG GCG GCC G    TGC GAG ACC GGC TAC CGG CTG GCG GCC G    TGC GAG ACT GGC TAC CGG CTG GCG GCC G    TGC GAG ACC GGC TAC CGG CTG GCG GCC G    Primers for replacing the Methionine at aa 388    Native Sequence    Pro His Glu Pro His Arg Cys Gln Met    CCC CAC GAG CCG CAC AGG TGC CAG ATG    CCC CAC GAG CCG CAC AGG TGC CAG CTG    Mutant Primer 1573         Leu    CCC CAC GAG CCG CAC AGG TGT CAA CAG    Mutant Primer 1583         Gln    CCC CAC GAG CCG CAC AGG TGC CAG GCC    Mutant Primer 1584         Ala    Phe Cys Asn Gln Thr Ala Cys Pro Ala    TTT TGC AAC CAG ACT GCC TGT CCA GCC G    TTT TGC AAC CAG ACT GCC TGT CCA GCC G    TTT TGC AAC CAG ACT GCC TGT CCA GCC G    TTT TGC AAC CAG ACT GCC TGT CCA GCC G    ______________________________________

                  TABLE 6    ______________________________________    Sample           Half-life (min)    ______________________________________    6h/227-462       2.7    HF treated 6h/227-462                     7.3    4t/227-462       8.1    ______________________________________

EXAMPLE 5 Expression of Recombinant Thrombomodulin Genes in CHO Cells

The cell line CHODXB11 was obtained from Larry Chasin of ColumbiaUniversity. Cells were grown in HAM's F-12 complete medium (GIBCO),supplemented with 9% fetal bovine serum (FBS) and gentamicin.

A. Transfection

Cells, ×10⁵, were plated in a 100 mm petri dish one day beforetransfection. A plasmid pTHR525 encoding a soluble TM analog wasprepared as described below in Example 9. The gene was constructed toencode an analog of thrombomodulin with the following modifications: δ3(truncated 3 amino acids from the natural amino terminus), Met388Leu(replacement of Methionine at position number 388 with Leucine),Arg456Gly (replacement of Arginine at position 456 with Glycine),His457Gln (replacement of Histidine at position 457 with Glutamine),Ser5474Ala (replacement of Serine at position 474 with Alanine), and δ7(truncated 7 amino acids from the carboxy terminus of a soluble TM at497, i.e., the analog would end at amino acid 490). For each dish, thepTHR525 DNA to be transfected (20 μg dissolved in 100 μl of Opti-MEM(BRL), supplemented with mercaptoethanol (1:1000 dilution)) was mixedwith a solution of Lipofectin (CalBiochem, 60 μg in 100 μl of Opti-MEM).The mixture was allowed to stand for 15 minutes at room temperature.Prior to the addition of the DNA mixture, the cells were washed twicewith Opti-MEM and 3 ml of Opti-MEM was placed in each dish. The DNA andLipofectin mixture was added to the plated cells and incubatedovernight. The media was then changed to HAM's F-12 selective media (w/oglycine, hypoxanthine, and thymidine) and the cells allowed to recoverovernight. The media was then changed to HAM's F-12 complete media withhygromycin (150 μg/ml, CalBiochem) and the cells maintained in thismedia for 3 days. At the end of this time, the media was changed toHAM's F-12 selective media (without glycine, hypoxanthine, andthymidine) supplemented with 9% dialyzed FBS and gentamicin. Clones wereallowed to generate (approximately seven to ten days) and the mixedpopulation was assayed by APC and ELISA assay. The cell population wasexpanded in culture flasks (225 cm²) for production purposes.

B. Production: (1 L Spinner Culture×2)

The cultures were started with 3 g Cytodex 3 microcarrier beads(Pharmacia), 500 ml HAM's F-12 complete medium supplemented with 5% FBS,and 8.4×10⁷ total cells. The following day, media was added to bring thevolume to 1 L. The supernatant was harvested every other day for about 6weeks. 450 ml was harvested the first two times and 1500 ml on allsubsequent occasions. The total harvest was 11.35 L and contained4.14×10⁶ U.

EXAMPLE 6 Purification of TM Analogs from Cultured Supernatants

A. Purification of TM_(LEO) (CHO)

Media containing the TM_(LEO) (CHO) analog with chondroitin or withoutsulfate expressed and secreted by CHO cells was made up to 0.01% Tween80, filtered (1.2 μM Serum Capsule #12168 and 0.2 μM Culture Capsule#12140, Gelman Sciences, Ann Arbor, Mich.), loaded on a 100 mlQ-Sepharose column, washed with 50 mM Tris-HCl pH 7.8, 0.2 M NaCl, 0.1mM EDTA, 0.01% Tween 80, and eluted with a NaCl gradient. (0.2 to 2M) inthe same buffer. Peak A (TM without chondroitin sulfate) and Peak B(with chondroitin sulfate) were diluted to 0.3M NaCl, 20 mM Tris-HCl,0.5 mM CaCl₂ EDTA, 0.02% NaN₃, pH 7.5. A thrombin affinitychromatography step is performed essentially as described above, and thesamples desalted. Active fractions were pooled.

B. Purification of-TM_(E) (Sf9).

These products can be isolated as described above or as follows:

All procedures were performed at 4° C. Filtered insect cell harvest wasdiluted 1:1 with water, titrated with acetic acid to pH 5.2 and loadedon a Q-Sepharose fast flow resin (25 mM Na-acetate, pH 5, 0.1M NaCl,0.02% NaN₃). Active fractions were eluted with 0.3M NaCl in the samebuffer, pooled, diluted to 0.3M NaCl, 20 mM Tris-HCl, 0.5 mM CaCl₂,0.02% NaN₃, adjusted to pH 7.5 (NaOH), loaded on a 120 mlDFP-inactivated thrombin Affigel-10 resin (described above) and elutedwith 2M NaCl, 20 mM Tris-HCl, 1 mM Na₂ EDTA, 0.02% NaN₃, pH 7.5. Activefractions were pooled, desalted and buffer exchanged on a Sephadex G-25column into 0.2% NEM-Ac, pH 7, loaded on a Mono-Q HR10/10 column(Pharmacia), and gradient eluted between 0 and 1M NaCl in the samebuffer. High specific activity fractions (APC assay) were pooled,desalted on Sephadex G-25 into PBS or 0.2% NEM-Ac, pH 7, and storedfrozen or lyophilized.

C. Soluble TM_(LEO) Expression in CHL1 Cells

DNA coding for both the wild type and M388L mutant forms of TM, aminoacids 1 to 497, and full length TM, amino acids 1 to 557, were expressedin Cos 7 and CHL1 cells using the mammalian expression vector pRc/CMV,obtained from Invitrogen, San Diego, Calif. For transient expression,Cos 7 cells expressing full length TM were harvested 48 to 72 h posttransfection. CHL1 cells are a human melanoma cell line, available fromthe ATCC.

D. Purification of TM_(LEO) (CHL1)

Media containing the TM_(LEO) (CHL1) analog with chondroitin sulfateexpressed and secreted by CHL1 cells was made 0.01% in Tween 80,filtered (1.2 μM Serum Capsule #12168 and 0.2 μM Culture Capsule #12140,Gelman Sciences, Ann Arbor, Mich.), loaded on a 100 ml Q-Sepharosecolumn, washed with 50 mM Tris-HCl pH 7.8, 0.2M NaCl, 0.1 mM EDTA, 0.01%Tween 80, and eluted with a NaCl gradient (0.2 to 2M) in the same buffer(elutes near 1M NaCl by APC assay). The eluent was diluted 3-fold withH₂ O, loaded on a second 5 ml Q-Sepharose column, washed with the samebuffer except with 0.001% Tween 80 and 0.7M NaCl and eluted with asecond shallow gradient (30 column volumes; 0.7 to 1.6M NaCl). Smallamounts (<500 μg) were further purified by molecular exclusionchromatography on Superose 6 (Pharmacia) in PBS.

E. Anion Exchange Chromatography

As noted above, more than one form of TM_(E) analog is detected inthrombin-affinity purified material from Sf9 cells run on a SDS-PAGE gelunder non-reducing conditions. A method was developed to resolve thesevariants. TM_(E) (Sf9) analog 6h/227-462, TM_(E) (Sf9) collected fromthe Sephadex G25 column, as described above, was applied to a Mono Qcolumn (Pharmacia, 10 micron particles, quaternary amine)pre-equilibrated with 0.2% N-ethylmorpholine (NEM) pH 7.0. After washingwith this buffer the various forms were separated using a gradient of 0to 0.4M NaCl. The elution and activity profiles are shown in FIG. 1.Samples of each fraction were evaluated on an SDS-PAGE gel undernon-reducing conditions. Three distinct bands with slightly differentmobilities could be seen on the stained gel. Fractions containingpeptides with like mobilities were pooled (A=fractions 32-35,B=fractions 40-44, C=fractions 70-71) and then assayed for total proteincontent and for activity in the Protein C activation assay. The specificactivities are listed in the table below. No inactive peptides weredetectable in any of the fractions.

    ______________________________________    Test Material  Specific Activity (U/mg)    ______________________________________    Mono Q Load    166,000 ± 12,000    fractions 32-35 (A)                   416,000 ± 19,000    fractions 40-44 (B)                   262,000 ± 4,000    fractions 70-71 (C)                   67,600 ± 5,000    ______________________________________

E. SDS-PAGE Analysis

Every fraction or every other fraction of TM_(E) (Sf9) purified on theMono-Q column was analyzed by SDS-PAGE as follows: 4.5 μl of a fractionwas mixed with 1.5 μl of 4 x concentrated SDS-PAGE sample buffer withoutreducing agents, heated about 10 to 15 min. at about 90° C. and loadedonto a 8-25% acrylamide Phast gel from Pharmacia using the comb andprotocol provided. The gel was run on the Phast gel system using theprotocol suggested by the manufacturer. The gel shows fractions acrossthe peak and shoulder which were pooled to make Pool and B, respectively(FIG. 2). The abbreviations are as follows:

Numbers--Fraction numbers referred to in FIG. 1 and above Table listingspecific activities.

A--occasionally seen artifact band in load on Panel A, frac. 28 andfrac. 39; this appears to be from protein from fingerprints on labware.

D--TME disulfide linked dimer which elutes in Pool C.

MU--upper monomer, this appears to be the single-chain TM_(E).

ML--lower monomer, has the same N-terminus as MU (AlaValValPro . . . ),but has a faster electrophoretic mobility as could be expected of aprotein proteolyzed near the C-terminus

L--material loaded on the Mono-Q column containing D, MU, and ML.

By pooling the fractions indicated in the above table, MU or ML can begreatly enriched, as desired.

EXAMPLE 7 Demonstration of the Presence of Two-Chain TM

A. Separation of Cleaved Forms from CHL1 and CHO Cells

The following samples were analyzed on an 8% Tris-Glycine gel from GelNovex, all samples were run under reducing conditions. FIG. 3 shows theresults for the following samples:

    ______________________________________    Lane    ______________________________________    1      Novex Wide Range Marker    2      TM.sub.LEO (CHO) #82891 LJ    3      TM.sub.LEO (CHO) PkB + Chondroitinase ABC (P. vulgaris)    4      TM.sub.LEO (CHO) PkB + Chondroitinase AC (Flavobacterium           heparium)    5      TM.sub.LEO (CHL1) PkB + Chondroitinase AC (Flavobacterium           heparium)    6      TM.sub.LEO (CHO) PkB + Chondroitinase AC (Anthrobackter           aurescens)    7      TM.sub.LEO (CHL1) PkB + Chondroitinase AC (Flavobacterium           heparium)    8      TM.sub.LEO (CHL1)PkB + Chondroitinase ABC (P. vulgaris)    9      TM.sub.LEO (CHL1) PkB #Q617    10     Novex Wide Range Markers    ______________________________________

This gel was originally run to test commercial chondroitinases fromvarious sources. It shows that samples from CHO cells and CHL1 cellsboth contain the 80 kDa band which appears to be the truncated form ofthe full length soluble TM analogs. The band at 66 kDa is BSA which isadded to the commercial chondroitinase preparations for stability. Lane9 is underloaded.

B. Western Blot

Samples of purified TM and TM analogs were analyzed on an 8%Tris-Glycine gel, which was run at 125 volts for 2 hours. The proteinswere electroblot-transferred to nitrocellulose for 3 hours at 120 MA.The nitrocellulose was then incubated overnight with 3% BSA at 4° C. Theblot was then exposed to a first mouse polyclonal antibody preparationwhich were raised against the reduced and denatured 6EGF region of TM,at a 1:500 dilution for 30 minutes. Then, a second antibody, acommercial biotinylated Goat was added for 30 minutes. The resultingnitrocellulose blot was then developed with avidin-HRP conjugate and4-Chloro-T-Naphthol, from a commercial supplier.

FIG. 4 shows a Western blot gel in which:

    ______________________________________    Lane    ______________________________________    1      10 μl BRL Biotinylated markers    2      TM.sub.LEO (CHL1) PkB #QG17 (-1250 APC Units)    3      TM.sub.LEO (CHO) PkB #82891 LJ (˜130 APC Units)    4      TM.sub.LEO (CHO) PkA #82891 LJ (˜125 APC Units)    5      TM.sub.LEO (CHL1) PkB + Chondroitinase ABC #QG21 (˜106           APC Units)    6      TM.sub.LEO (CHO) PkB + Chondroitinase ABC #QG39 (˜34           APC Units)    7      TM.sub.LEO (CHL1) PkB + Chondroitinase ABC #QG41 (˜100           APC Units)    8      5 μl "Rainbow" markers, Amersham    ______________________________________    MW    Markers       BRL    for FIG. 4;   Biotinylated                            "Rainbow"    ______________________________________                      97.4   kDa  200  kDa                      66.2        97.4                      42.7        69.0                      31.0        46.0     Run with          21.5        21.5          Run w/    Dye Front         14.4        14.3          Dye Front    ______________________________________

This Western analysis shows that all samples of TM_(LEO) expressed inCHO cells have an immunoreactive band at 80 kDa which appears to be thetruncated from of TM and that some sample of TM_(LEO) expressed in CHL1cells have the 80 kDa band (Lane 2). Lane 7 containing the "lectin-6EGF"analog, TM_(LE) is underloaded.

D. K_(d) Determination

The K_(d) was determined for isolated preparations of recombinantthrombomodulin. TM_(LEO) (CHO) was prepared as described earlier.Determinations were made in 96 well plates in an assay diluent (20 mMTris-HCl, pH 7.5, 0.1M NaCl, 0.1% NaN₃, 0.5% BSA, containing either 0.25or 2.5 mM CaCl₂). For the K_(d) determination, thrombin (1 nM) was addedto the TM analog (0.5 to 250 nM); reaction was initiated by Protein Caddition (3 μM). All concentrations listed are final concentrations.Mixtures were incubated 10-60 minutes (75 μl , 20° C.) and quenched withhirudin (570 nM). 100 μl/well of S-2266 substrate (Kabi Vitrum), inmodified assay diluent, was then added (2 mM).

As can be seen from the double reciprocal plot in FIG. 5, the actualfirst point, corresponding to high TM concentration, is displaced fromthe linear projection derived from the measurements at lower TMconcentrations. This indicates that another TM component with asignificantly high K_(d) is present in the test sample. It appears thatthere are two classes of thrombin binding species in the sample, both ofwhich lead to the formation of an active complex. The low affinity formis likely to correspond to the cleaved or truncated form, e.g., a TManalog which does not bind thrombin as tightly as uncleaved TM.

EXAMPLE 8 Sequencing Data Demonstrating Two Different Amino Termini

A. N-terminal Sequence Analysis

The purified protein was dried and sequenced (Applied Biosystems, Model#477 with a 900A data module or Model #470A with chart recorder).PTH-amino acids were identified on a 120A Applied Biosystems PTHAnalyzer by RP-HPLC (Brownlee PTH-C18 cartridge, 2.1×222 mm).

B. N-terminal Analysis

Various preparations of TM analogs were analyzed as above. As can beseen in Table 7, the samples from TM_(LEO) (CHO) peak A containheterogeneous N-termini. For example, N-terminal analysis of 3 samplesshown in Table 7 of TM produced by a plasmid containing the unmodifiedsequence expressed in CHO cells showed a strong cleavage site sequenceamounting to 5 to 19% (11±4%) of the protein present.

In contrast, N-terminal analysis of at least 100 picomole of DXB-11 525,a TM preparation isolated from CHO cells transformed with the pTHR525plasmid containing the TM mutations at the indicated positions(δ63,M388L,R456G,H457Q,S474A,δ7) confirmed that this poly-peptidecontained essentially no N-terminal heterogeneity (maximum secondsequence is 0.6±1.350 ≅0%). In particular, no secondary amino terminuscorresponding to a natural sequence of :HIGT was thus indicating absenceof detectable protease cleavage at that, or any other, site.

                  TABLE 7a    ______________________________________    Sequence Comparison of Samples of TM.sub.LEO (CHO)PkA with    TM.sub.LEO (CHO)∂3,M388L,R456G,H457Q1S474A,∂7    Cycle  N-term#1  N-term#2 Sum    Clip   %    ______________________________________    A) Sample: TM.sub.LEO (CHO)PkA 82891; 10/23/91    1      Ala 110   Phe 57   167    His 0.6    2      Pro --    Pro --   115    Ile 11 9.5%    3      Ala --    Ala --   127    Gly 24 18.9%    4      Glu 30    Pro 49   79     Thr 1.0                                            12.6%    5      Pro 72    Ala 71   143    Asp 7.1                                            5.0%    6      Gln 41    Glu 26   67     Cys --    7      Pro --    Pro --   86     Asp 8.5                                            9.9%    B) Sample: TM.sub.LEO (CHO)PkA 91991; 10/28/91    1      Ala 221   Phe 108  329    His 8    2      Pro --    Pro --   228    Ile 13 5.7%    3      Ala --    Ala --   321    Gly 37 11.5%    4      Glu 128   Pro 114  242    Thr 7    5      Pro 182   Ala 125  307    Asp 40 13%    6      Gln 147   Glu 114  67     Cys --    7      Pro --    Pro --   328    Asp 126    C) Sample: TM.sub.LEO (CHO)PkA 102491-A; 1/17/92    1      Ala 142   Phe 60   202    His 0  0%    2      Pro --    Pro --   118    Ile 20 17%    3      Ala --    Ala --   160    Gly 20 12.5%    4      Glu 48    Pro 38   86     Thr 8  9.3%    5      Pro 48    Ala 60   108    Asp 41    6      Gln 52    Glu 39   91     Cys --    7      Pro --    Pro --   58     Asp 42    ______________________________________     Notes:     1) Data is pmol of amino acid per cycle and percent clipped calculated pe     cycle.     2) Amino acids which are difficult to quantitate reliably: His, Arg, Ser,     Thr     3) Cys not quantitated since samples not reduced and alkylated.     4) Pro often not well cleaved, therefore yield may be low.     5) Pmol data corrected for background signal and "lag" signal from     previous cycles.

                  TABLE 7b    ______________________________________    D) Sample: TM.sub.LEO (CHO)∂3,M388L,R456G,H457Q,S474A.differe    ntial.7,pTHR525    Cycle       N-term      Clip       %    ______________________________________    1           Glu 88      Gln 0      0%    2           Pro 184     Ile 0.4    0.2%    3           Gln 171     Gly 6      3.5%    4           Pro 172     Thr 0      0%    5           Gly 149     Asp 0      0%    6           Gly 143     Cys --    7           Ser 28      Asp 0      0%    ______________________________________

EXAMPLE 9 Method of Mutagenesis and Oligonucleotide Selection forProduction of Protease-Resistant TM Analogs

The plasmid pTHR525, coding for a preferred embodiment of aprotease-resistant TM, was constructed by mutagenesis of the TM gene(see U.S. patent application Ser. No. 07/345,372, GenBank®, or thesequence of pTHR324 shown in Table 8; pTHR324 contains the TM gene inthe pRC/CMV vector). A gene construct which, upon expression, expressesa polypeptide corresponding to amino acids 3-490 was made by standardmutagenesis techniques.

                                      TABLE 8    __________________________________________________________________________    GCGGCCGC    tcgagcatgcatctagagggccctatt    ctatagtgtcacctaaatgctcgctgatcagcctcgactgtgccttctagttgccagccatctgttgtttgccc    ctcccc    cgtgccttccttgaccctgg    aaggtgccactcccactgtcctttcctaataaaatgaggaaattgcatcgcattgtctgagtaggtgtcattct    attctg    gggggtggggtggggcagga    cagcaagggggaggattgggaagacaatagcaggcatgctggggatgcggtgggctctatggaaccagctgggg    ctcgag    gggggatccccacgcgccct    gtagcggcgcattaagcgcggcgggtgtggtggttacgcgcagcgtgaccgctacacttgccagcgccctagcg    cccgct    cctttcgctttcttcccttc    ctttctcgccacgttcgccggctttccccgtcaagctctaaatcggggcatccctttagggttccgatttagtg    ctttac    ggcacctcgaccccaaaaaa    cttgattagggtgatggttcacgtagtgggccatcgccctgatagacggtttttcgcctttactgagcactctt    taatag    tggactcttgttccaaactg    gaacaacactcaaccctatctcggtctattcttttgatttataagatttccatcgccatgtaaaagtgttacaa    ttagca    ttaaattacttctttatatg    ctactattcttttggcttcgttcacggggtgggtaccgagctcgaattctgtggaatgtgtgtcagttagggtg    tggaaa    gtccccaggctccccaggca    ggcagaagtatgcaaagcatgcatctcaattagtcagcaaccaggtgtggaaagtccccaggctccccagcagg    cagaag    tatgcaaagcatgcatctca    attagtcagcaaccatagtcccgcccctaactccgcccatcccgcccctaactccgcccagttccgcccattct    ccgccc    catggctgactaattttttt    tatttatgcagaggccgaggccgcctcggcctctgagctattccagaagtagtgaggaggcttttttggaggcc    taggct    tttgcaaaaagctcccggga    gcttggatatccattttcggatctgatcaagagacaggatgaggatcgtttcgcatgattgaacaagatggatt    cacgc    aggttctccggccgcttggg    tggagaggctattcggctatgactgggcacaacagacaatcggctgctctgatgccgccgtgttccggctgtca    gcgcag    gggcgcccggttctttttgt    caagaccgacctgtccggtgccctgaatgaactgcaggacgaggcagcgcggctatcgtggctggccacgacgg    gcgttc    cttgcgcagctgtgctcgac    gttgtcactgaagcgggaagggactggctgctattgggcgaagtgccggggcaggatctcctgtcatctcacct    tgctcc    tgccgagaaagtatccatca    tggctgatgcaatgcggcggctgcatacgcttgatccggctacctgcccattcgaccaccaagcgaaacatcgc    atcgag    cgagcacgtactcggatgga    agccggtcttgtcgatcaggatgatctggacgaagagcatcaggggctcgcgccagccgaactgttcgccaggc    tcaagg    cgcgcatgcccgacggcgag    gatctcgtcgtgacccatggcgatgcctgcttgccgaatatcatggtggaaaatggccgcttttctggattcat    cgactg    tggccggctgggtgtggcgg    accgctatcaggacatagcgttggctacccgtgatattgctgaagagcttggcggcgaatgggctgaccgcttc    ctcgtg    ctttacggtatcgccgctcc    cgattcgcagcgcatcgccttctatcgccttcttgacgagttcttctgagcgggactctggggttcgaaatgac    cgacca    agcgacgcccaacctgccat    cacgagatttcgattccaccgccgccttctatgaaaggttgggcttcggaatcgttttccgggacgccggctgg    atgatc    ctccagcgcggggatctcat    gctggagttcttcgcccaccccaacttgtttattgcagcttataatggttacaaataaagcaatagcatcacaa    atttca    caaataaagcatttttttca    ctgcattctagttgtggtttgtccaaactcatcaatgtatcttatcatgtctggatcccgtcgacctcgagagc    ttggcg    taatcatggtcatagctgtt    tcctgtgtgaaattgttatccgctcacaattccacacaacatacgagccggaagcataaagtgtaaagcctggg    gtgcct    aatgagtgagctaactcaca    ttaattgcgttgcgctcactgcccgctttccagtcgggaaacctgtcgtgccagctgcattaatgaatcggcca    acgcgc    ggggagaggcggtttgcgta    ttgggcgctcttccgcttcctcgctcactgactcgctgcgctcggtcgttcggctgcggcgagcggtatcagct    cactca    aaggcggtaatacggttatc    cacagaatcaggggataacgcaggaaagaacatgtgagcggggggccggcaaaaggccaggaaccgtaaaaagg    ccgcgt    tgctggcgtttttccatagg    gacggatcgggagatctcccgatcccctatggtcgactctcagtacaatctgctctgatgccgcatagttaagc    cagtat    ctgctccctgcttgtgtgtt    ggaggtcgctgagtagtgcgcgagcaaaatttaagctacaacaaggcaaggcttgaccgacaattgcatgaaga    atctgc    ttagggttaggcgttttgcg    ctgcttcgcgatgtacgggccagatatacgcgttgacattgattattgactagttattaatagtaatcaattac    ggggtc    attagttcatagcccatata    tggagttccgcgttacataacttacggtaaatggcccgcctggctgaccgcccaacgacccccgcccattgacg    tcaata    atgacgtatgttcccatagt    aacgccaatagggactttccattgacgtcaatgggtggactatttacggtaaactgcccacttggcagtacatc    aagtgt    atcatatgccaagtacgccc    cctattgacgtcaatgacggtaaatggcccgcctggcattatgcccagtacatgaccttatgggactttcctac    ttggca    gtacatctacgtattagtca    tcgctattaccatggtgatgcggttttggcagtacatcaatgggcgtggatagcggtttgactcacggggattt    ccaagt    ctccaccccattgacgtcaa    tgggagtttgttttggcaccaaaatcaacgggactttccaaaatgtcgtaacaactccgccccattgacgcaaa    tgggcg    gtaggcgtgtacggtgggag    gtctatataagcagagctctctggctaactagagaacccactgcttaactggcttatcgaaattaatacgactc    actata    gggagaccgg    AAGCTTCCTCGAGCGATATCGCCGCGGCATCGATCGGGCCCGAGATCTCGCGCGCCTGGGTAACATGCTTGGGG    TCCTGG    TCCTTGGCGCGCTGG    CCCTGGCCGGCCTGGGGTTCCCCGCACCCGCAGAGCCGC    AGCCGG    GTGGCAGCCAGTGCGTCGAGCACGACTGCTTCGCGCTCTACCCGGGCCCCGCGAC    CTTCCTCAATGCCAGTCAGATCTGCGACGGACTGCGGGGCCACCTAATGA    CAGTGCGCTCCTCGGTGGCTGCCGATGTCATTTCCTTGCTACTGA    ACGGCGACGGCGGCGTTGGCCGCCGGCGCCTCTGGATCGGCCTGCAGCTGCCACCCGGCTGCGGCGACCCCAAG    CGCCTC    GGGCCCCTGCGCGGCTTCCAGTGGGTTACGGGAGACAACAACACCAGCTATAGCAGGTGGGCACGGCTCGACCT    CAATGG    GGCTCCCCTCTGCGGCCCGTTGTGCGTCGCTGTCTCCGCTGCTGAGGCCACTGTGCCCAGCGAGCCGATCTGGG    AGGAGC    AGCAGTGCGAAGTGAAGGCCGATGGCTTCCTCTGCGAGTTCCACTTCCCAGCCACCTGCAGGCCACTGGCTGTG    GAGCCC    GGCGCCGCGGCTGCCGCCGTCTCGATCACCTACGGCACCCCGTTCGCGGCCCGCGGAGCGGACTTCCAGGCGCT    GCCGGT    GGGCAG    CTCCGCCGCGGTGGCTCCCCTCGGCTTACAGCTAATGTGCACCGCGCCGCCCGGAGCGGTCCAGGGGCACTGGG    CCAGGG    AGGCGCCGGGCGCTTGGGACTGCAGCGTGGAGAACGGCGG    CTGCGA    GCACGCGTG    CAATGCGATCCCTGGGGCTCCC    CGCTGC    GAGTGCCCAGCCGGCGCCGCCCTGCAGGCAGACGGGCGCTCCTGCACCGCATCCGCGACGCAGTCCTGCAACGA    CCTCTG    CGAGCACTTCTGCGTTCCCAACCCGACCAGCCGGGCTCCTACTCGTGCATGTGCGAGACCGGCTACCGGCTGGC    GCCGACCAACACCGGTGCGAGGACGTGGATGACTGCATACTGGAGCCCAGTCCGTGTCCGCAGCGCTGTGTCAA    CACACA    GGGTGGCTTCGAGTGCCACT    GCTACCCTAACTACGACCTGGTGGACGGCGAGTGTGTGGAGCCCGTGGACCCGTGCTTCAGAGCCAACTGCGAG    TACCAG    TG    CCAGCCCCTGAACCAAACTAGCTACCTCTGCGTCTGCGCCGAGGGCTTCGCGCCCATTCCCCACGAGCCGCACA    GGTGCC    AGATGTTTTGCAACCAGACT    GCCTGTCCAGCCGACTGCGACCCCAACACCCAGGCTAGCTGTGAGTGCCCTGAAGGCTACATCCTGGACGACGG    TTTCAT    CTGCACGGACATCGACGAGT    GCGAAAACGGCGGCTTCTGCTCCGGGGTGTGCCACAACCTCCCCGGTACCTTCGAGTGCATCTGCGGGCCCGAC    TCGGCC    CTTGCGCGCCACATTGGCAC    CGACTGTGACTCCGGCAAGGTGGACGGTGGC    GACAGC    GGCTCTGGCGAGCCCCGCCCAGCCCGACGC    CCGGCT    CCACCTTGACTCCTCCGGCCGTGGGGCTCGTGCATTGGTGA    ctccgcccccctgacgagcatcacaaaaatcgacgctcaagtcagaggtggcgaaacccgacaggactataaag    atacca    ggcgtttccccctggaagct    ccctcgtgcgctctcctgttccgaccctgccgcttaccggatacctgtccgcctttctcccttcgggaagcgtg    gcgctt    tctcaatgctcacgctgtag    gtatctcagttcggtgtaggtcgttcgctccaagctgggctgtgtgcacgaaccccccgttcagcccgaccgct    gcgcct    tatccgtaactatcgtctt    gagtccaacccggtaagacacgacctatcgccactggcagcagccactggtaacaggattagcagagcgaggta    tgtagg    cgtgctacagagttcttga    agtggtggcctaactacggctacactagaaggacagtatttggtatctgcgctctgctgaagccagttaccttc    ggaaaa    agattggtagctcttgatc    cggcaaacaaaccaccgctggtagcggtggtttttttgtttgcaagcagcagattacgcgcagaaaaaaaggat    ctcaag    aagatcctttgatcttttct    acggggctcacgctcagtggaacgaaaactcacgttaagggattttggtcatgagattatcaaaaaggatcttc    accta    gatccttttaaattaaaaat    gaagttttaaatcaatctaaagtatatatgagtaaacttggtctgacagttaccaatgcttaatcagtgaggca    cctatc    tcagcgatctgtctatttcg    ttcatccatagttgcctgactccccgtcgtgtagataactacgatacgggagggcttaccatctggccccagtg    ctgcaa    tgataccgcgagacccacgc    tcaccggctccagatttatcagcaataaaccagccagccggaagggccgagcgcagaagtggtcctgcaacttt    atccgc    ctccatccagtctattaatt    gttgccgggaagctagagtaagtagttcgccagttaatagtttgcgcaacgttgttgccattgctacaggcatc    gtggtg    tcacgctcgtcgtttggtat    ggcttcattcagctccggttcccaacgatcaaggcgagttacatgatcccccatgttgtgcaaaaaagcggtta    gctcct    tcggtcctccgatcgttgtc    agaagtaagttggccgcagtgttatcactcatggttatggcagcactgcataattctcttactgtcatgccatc    cgtaag    atgcttttctgtgactggtg    agtactcaaccaagtcattctgagaatagtgtatgcggcgaccgagttgctcttgcccggcgtcaatacgggat    aatacc    gcgccacatagcagaacttt    aaaagtgctcatcattggaaaacgttcttcggggcgaaaactctcaaggatcttaccgctgttgagatccagtt    cgatgt    aacccactcgtgcacccaac    tgatcttcagcatcttttactttcaccagcgtttctgggtgagcaaaaacaggaaggcaaaatgccgcaaaaaa    gggaat    aagggcgacacggaaatgtt    gaatactcatactcttcctttttcaatattattgaagcatttatcagggttattgtctcatgagcggatacata    tttgaa    tgtatttagaaaaataaaca    aataggggttccgcgcacatttccccgaaaagtgccacctgacgtc    __________________________________________________________________________     *HIND3-NOT1 fragment from pTHR322 containing the DNFL TM gene into the     HIND3NOT 1 sites of pRcCMV for expression of DNFL in COS1 cells.

A. Modification of the Protease Cleavage Site

The Arg⁴⁵⁶ His⁴⁵⁷ →Gly⁴⁵⁶ /Gln⁴⁵⁷ mutation was constructed as disclosedin Example 1(C) using as a primer oligomer COD-2218.

B. Modification of the O-linked Chondroitin Sulfate Linkage Site

The Ser⁴⁷⁴ →Ala⁴⁷⁴ mutation was constructed as disclosed in Example 1(C)using as a primer oligomer COD-1886.

C. Modification of the N-terminus

The N-terminal deletion of the first three amino acids of native TM,which has a heterogeneous signal sequence cleavage site, was constructedas disclosed in Example 1(C) using as a primer oligomer COD-2321. Theconstruct has a change in the fourth glycine of the signal sequence(i.e., amino acid -3) from Gly to Val, in addition to providing anN-terminal sequence, after processing of the signal sequence, whichbegins at amino acid Gly4. This construct was prepared based uponpredictions of signal cleavage efficiencies using algorithms describedin von Heijne, G., Nucleic Acids Res. 14 4683 (1986).

D. Modification of the C-terminus

The C-terminal deletion of the terminal 7 amino acids of the TM_(LEO)polypeptide to produce a polypeptide ending at amino acid 490 of TM(with reference to the native human protein) to produce anexoprotease-resistant Pro-Pro sequence C-terminus was constructed asdisclosed in Example 1(C) using as a primer oligomer COD-2320. A summaryof the modifications to the C-terminus is shown in Table 9.

E. Summary of the Construction of pTHR525

The starting plasmid, PCDM8, for the following constructs was obtainedfrom Invitrogen, San Diego, Calif. It carries the cytomegalovirusimmediate early promoter. pTHR219 was cut with and the MluI-NotIfragment isolated. This fragment was inserted into pTHR211 yieldingpTHR253. pTHR253 was mutagenized with COD2218 to convert R456G andH457Q, yielding pTHR491. pTHR491 was cut and the Kpn-NotI fragmentisolated. This fragment was inserted into the Kpn-NotI site of pTHR470,carrying the S474A mutation yielding pTHR496. This plasmid contains themutations S474A, R456G, and H457Q. pTHR496 was cut and the MluI-NotIfragment isolated. This fragment was inserted into the Mlu1-Not1 site ofpTHR235 yielding pTHR511. This plasmid contains the mutations S474A,R456G, H457Q, and the upstream TM sequences from the NotI site. pTHR511was mutagenized with COD2320 to remove the 7 C-terminal amino acidsyielding pTHR514. pTHR514 was cut and the MluI-NotI fragment isolated.This fragment was inserted into pTHR518 yielding pTHR524. pTHR518 wasconstructed by inserting the ClaI-SmaI fragment from pTHR515 intopTHR512. pTHR524 was cut and the XbaI-NotI fragment isolated. Thisfragment was inserted into pTHR495 at the XbaI-NotI site yieldingpTHR525. pTHR525 is expressed to make one of the preferredthrombomodulin analogs having N-terminal δ3, R456G, H457Q, S474A, andC-terminal δ7. ##STR44##

Table 8A-8G shows sequences from the various intermediate plasmidconstructs.

Table 9A shows the sequences of the various primers used to mutagenizethe plasmids.

The preceding examples can be repeated with similar success bysubstituting the generically or specifically described reactants and/oroperating conditions of this invention for those used in the precedingexamples.

From the foregoing description, one skilled in the art can easilyascertain the essential characteristics of this invention, and withoutdeparting from the spirit and scope thereof, can make various changesand modifications of the invention to adapt it to various usages andconditions. ##STR45##

                                      TABLE 8B    __________________________________________________________________________     ##STR46##     ##STR47##     ##STR48##     ##STR49##     ##STR50##     ##STR51##    __________________________________________________________________________

                                      TABLE 8C    __________________________________________________________________________     ##STR52##     ##STR53##    __________________________________________________________________________

                                      TABLE 8D    __________________________________________________________________________     ##STR54##     ##STR55##     ##STR56##     ##STR57##     ##STR58##     ##STR59##     ##STR60##    __________________________________________________________________________

                                      TABLE 8E    __________________________________________________________________________    GCTGCGCTCGGTCGTTCGGCTGCGGCGAGCGGTATCAGCTCACTCAAAGGCGGTAATACG     ##STR61##     ##STR62##     ##STR63##    __________________________________________________________________________

                                      TABLE 8F    __________________________________________________________________________     ##STR64##     ##STR65##     ##STR66##     ##STR67##     ##STR68##     ##STR69##     ##STR70##     ##STR71##    __________________________________________________________________________

                                      TABLE 8G    __________________________________________________________________________    pTHR525.seq     ##STR72##    pTHR525.seqA     ##STR73##    __________________________________________________________________________

                                      TABLE 9A    __________________________________________________________________________     ##STR74##     ##STR75##     ##STR76##     ##STR77##     ##STR78##     ##STR79##    __________________________________________________________________________

                                      TABLE 9B    __________________________________________________________________________     ##STR80##     ##STR81##     ##STR82##     ##STR83##     ##STR84##    __________________________________________________________________________

What is claimed is:
 1. A DNA sequence coding for a thrombomodulinprotein analog, wherein the amino acid sequence of a protease cleavagesite is modified by substitution or deletion of an amino acid at theprotease cleavage site, whereby the analog is resistant to proteasecleavage at that site and wherein the analog has at least 50% of theability to potentiate thrombin-mediated activation of protein C as saiduncleaved protein without said modification at the protease cleavagesite.
 2. A vector comprising a DNA sequence of claim 1, operably linkedto a promoter sequence capable of being expressed in a suitable host. 3.A vector of claim 2 capable of being expressed in a CHO cell.
 4. A DNAsequence of claim 1, further wherein the O-linked glycosylation domainis modified by substitution or deletion of an amino acid residue forminga glycosylation site, whereby addition of glycosaminoglycan to a serineor threonine residue in the O-linked glycosylation domain is attenuated,said analog having at least 50% of the ability to potentiatethrombin-mediated activation of protein C and a reduced ability toinactivate thrombin-mediated conversion of fibrinogen to fibrin, eachability as compared with native thrombomodulin.
 5. A DNA sequence ofclaim 4, further wherein an oxidation-sensitive methionine at a positioncorresponding to the methionine at position 388 of native thrombomodulinis modified by substitution or deletion, whereby the analog is resistantto oxidation inactivation at said methionine residue, and wherein theanalog has at least 50% of the ability to potentiate thrombin-mediatedactivation of protein C as the unoxidized protein having a methionineresidue at that position.
 6. A DNA sequence of claim 5, further whereinthe amino acid sequence of the N-terminus is modified by substitution ordeletion of one or more amino acids at the N-terminus to prevent signalsequence cleavage heterogeneity, whereby the analog has a singleN-terminus.
 7. A DNA sequence of claim 6, further wherein the amino acidsequence of the C-terminus is modified in the O-linked glycosylationdomain by substitution or deletion of one or more amino acids to providea C-terminus resistant to exoproteolytic cleavage, whereby the analoghas a single C-terminus.
 8. A DNA sequence of claim 6, which codes for athrombomodulin analog having the amino acid sequence of nativethrombomodulin modified at the following positions:removal of aminoacids 1-3,M388L, R456G, H457Q, S474A, and terminating at P490.
 9. A DNAsequence of claim 1, further wherein an oxidation-sensitive methionineat a position corresponding to the methionine at position 388 of nativethrombomodulin is modified by substitution or deletion, whereby theanalog is resistant to oxidation inactivation at said methionineresidue, and wherein the analog has at least 50% of the ability topotentiate thrombin-mediated activation of protein C as the unoxidizedprotein having a methionine residue at that position.
 10. A DNA sequencecoding for a thrombomodulin protein analog, wherein the amino acidsequence of the N-terminus is modified by substitution or deletion ofone or more amino acids at the N-terminus to prevent signal sequencecleavage heterogeneity, whereby the analog has a single N-terminus,wherein said analog comprises a polypeptide having an amino acidsequence corresponding to the lectin binding, EGF and O-linkedglycosylation domains of native thrombomodulin, and wherein the analoghas at least 50% of the ability to potentiate thrombin-mediatedactivation of protein C as said protein having a native thrombomodulinN-terminus.
 11. A vector comprising a DNA sequence of claim 10 operablylinked to a promoter sequence capable of being expressed in a suitablehost.
 12. A vector of claim 11, capable of being expressed in a CHOcell.
 13. A DNA sequence coding for a thrombomodulin protein analog,wherein the amino acid sequence of the C-terminus is modified bysubstitution or deletion of one or more amino acids to provide aC-terminus resistant to exoproteolytic cleavage, whereby the analog hasa single C-terminus, and wherein the analog has at least 50% of theability to potentiate thrombin-mediated activation of protein C as saidprotein having a native thrombomodulin C-terminus.
 14. A vectorcomprising a DNA sequence of claim 13, operably linked to a promotersequence capable of being expressed in a suitable host.
 15. A vector ofclaim 14, capable of being expressed in a CHO cell.
 16. A method ofexpressing a single-chain thrombomodulin analog in a cell which producesa protease which cleaves said thrombomodulin analog, comprising:a)detecting the presence of cleaved thrombomodulin analog in theexpression product; b) determining the protease cleavage site by aminoacid sequence analysis; c) modifying the nucleotide sequence of the genewhich codes for the thrombomodulin analog by substitution or deletion ofone or more nucleotides coding for an amino acid at the cleavage site,whereby the thus-produced thrombomodulin analog is resistant to proteasecleavage at said site and maintains at least 50% of the ability topotentiate thrombin-mediated activation of protein C as nativethrombomodulin; d) expressing the modified thrombomodulin analog gene ina cell which produces the protease; and e) isolating the thus-producedsingle-chain thrombomodulin analog.
 17. A method of claim 16, whereinthe cleaved thrombomodulin analog lacks the ability to potentiatethrombin-mediated activation of protein C as the uncleaved nativethrombomodulin and/or is a competitive inhibitor of the uncleaved nativethrombomodulin.